Method and device for providing control information for uplink transmission in wireless communication system supporting uplink multi-antenna transmission

ABSTRACT

The present invention relates to a wireless communication system, and more particularly, a method and device providing control information for uplink transmission in a wireless communication system supporting uplink multi-antenna transmission. An uplink multi-antenna transmission scheduling method, according to one embodiment of the present invention, comprises the following steps: creating downlink control information (DCI), which includes precoding information showing a transmission rank and a precoding matrix of an uplink transmission; transmitting said created downlink control information, which schedules the transmission of an uplink, through a downlink control channel; and receiving said uplink transmission, which is scheduled according to said downlink control information, through an uplink data channel, wherein the size of said precoding information can be determined with respect to the available number of precoding matrices, according to the number of said multi-antennas and uplink transmission rank.

TECHNICAL FIELD

The present invention relates to a wireless communication system, andmore particularly, to a method and apparatus for providing controlinformation for uplink transmission in a wireless communication systemsupporting uplink multi-antenna transmission.

BACKGROUND ART

Single Carrier-Frequency Division Multiple Access (SC-FDMA) is employedas an uplink multiple access scheme in the 3^(rd) Generation PartnershipProject Long Term Evolution (3GPP LTE) standard (e.g. release 8 or 9).Introduction of clustered Discrete Fourier Transform-spread-OrthogonalFrequency Division Multiplexing (DFT-s-OFDMA) as an uplink multipleaccess scheme is under discussion in the 3GPP LTE-Advanced (LTE-A)standard (e.g. release 10) being an evolution of the 3GPP LTE standard.Uplink/downlink transmission in a single carrier band is supported inthe 3GPP LTE standard and uplink transmission through a plurality ofcarriers (i.e. carrier aggregation) is under discussion in the 3GPPLTE-A standard. In addition, while the 3GPP LTE standard support uplinktransmission from a User Equipment (UE) through a single Transmission(Tx) antenna, the 3GPP LTE-A standard discusses support of uplinktransmission from a UE through a plurality of Tx antennas (uplinkmulti-antenna transmission) in order to increase uplink transmissionthroughput.

Multi-antenna transmission is also called Multiple Input Multiple Output(MIMO). MIMO can increase the efficiency of data transmission andreception using multiple Tx antennas and multiple Reception (Rx)antennas. MIMO schemes include spatial multiplexing, transmit diversity,beamforming, etc. A MIMO channel matrix formed according to the numberof Rx antennas and the number of Tx antennas can be decomposed of aplurality of independent channels and each independent channel is calleda layer or a stream. The number of layers or streams or a spatialmultiplexing rate is called a rank.

A multi-transmission stream or multi-layer transmission scheme may beapplied to a UE for the purpose of spatial multiplexing, as an uplinkmulti-antenna transmission technology. This scheme is called SingleUser-MIMO (SU-MIMO). To maximize the capacity of a transmission channelin uplink SU-MIMO, a precoding weight may be used. This may be referredto as precoded spatial multiplexing.

DISCLOSURE Technical Problem

An object of the present invention devised to solve the conventionalproblem is to provide a method for configuring a control signal in orderto effectively support uplink multi-antenna transmission. Moreparticularly, the present invention is intended to provide a method forindicating whether an uplink Transport Block (TB) is disabled by controlinformation that schedules uplink multi-antenna transmission and amethod for representing precoding information for use in uplinkmulti-antenna transmission.

It will be appreciated by persons skilled in the art that the objectsthat could be achieved with the present invention are not limited towhat has been particularly described hereinabove and the above and otherobjects that the present invention could achieve will be more clearlyunderstood from the following detailed description.

Technical Solution

In an aspect of the present invention, a method for scheduling uplinkmulti-antenna transmission includes generating Downlink ControlInformation (DCI) including precoding information indicating atransmission rank and a precoding matrix for uplink transmission,transmitting the generated DCI for scheduling uplink transmission on adownlink control channel, and receiving an uplink signal scheduledaccording to the DCI on an uplink data channel. The size of theprecoding information is determined according to the number of multipleantennas and the number of precoding matrices available according to anuplink transmission rank.

In another aspect of the present invention, a method for performinguplink multi-antenna transmission includes receiving DCI includingprecoding information on a downlink control channel, the precodinginformation indicating a transmission rank and a precoding matrix foruplink transmission, and transmitting an uplink signal scheduledaccording to the DCI on an uplink data channel. The size of theprecoding information is determined according to the number of multipleantennas and the number of precoding matrices available according to anuplink transmission rank.

In another aspect of the present invention, a base station forscheduling uplink multi-antenna transmission includes a transmissionmodule for transmitting a downlink signal to a user equipment, areception module for receiving an uplink signal from the user equipment,and a processor for controlling the base station including the receptionmodule and the transmission module. The processor is configured togenerate DCI including precoding information indicating a transmissionrank and a precoding matrix for uplink transmission, transmit thegenerated DCI for scheduling uplink transmission on a downlink controlchannel through the transmission module, and receive an uplink signalscheduled according to the DCI on an uplink data channel through thereception module. The size of the precoding information is determinedaccording to the number of multiple antennas and the number of precodingmatrices available according to an uplink transmission rank.

In a further aspect of the present invention, a user equipment forperforming uplink multi-antenna transmission includes a transmissionmodule for transmitting an uplink signal to a base station, a receptionmodule for receiving a downlink signal from the base station, and aprocessor for controlling the user equipment including the transmissionmodule and the reception module. The processor is configured to receiveDCI including precoding information on a downlink control channelthrough the reception module, the precoding information indicating atransmission rank and a precoding matrix for uplink transmission andtransmit an uplink signal scheduled according to the DCI on an uplinkdata channel through the transmission module. The size of the precodinginformation is determined according to the number of multiple antennasand the number of precoding matrices available according to an uplinktransmission rank.

The followings may be applied commonly to the embodiments of the presentinvention.

If the number of multiple antennas is 2, the size of the precodinginformation may be 3 bits and if the number of multiple antennas is 4,the size of the precoding information may be 6 bits.

The precoding information may indicate a different transmission rank anda different precoding matrix according to the number of enabledcodewords.

For 2 multiple antennas, if one codeword is enabled, the precodinginformation may include 6 states indicating 6 precoding matrices forrank 1 and 2 reserved states, and if two codewords are enabled, theprecoding information may include 1 state indicating 1 precoding matrixfor rank 2 and 7 reserved states.

For 4 multiple antennas, if one codeword is enabled, the precodinginformation may include 24 states indicating 24 precoding matrices forrank 1, 16 states indicating 16 precoding matrices for rank 2, and 24reserved states, and if two codewords are enabled, the precodinginformation may include 16 state indicating 16 precoding matrix for rank2, states indicating 12 precoding matrices for rank 3, 1 stateindicating 1 precoding matrix for rank 4, and 35 reserved states.

The downlink control channel may be a Physical Downlink Control Channel(PDCCH) and the uplink data channel may be a Physical Uplink SharedChannel (PUSCH).

The above overall description and a later detailed description of thepresent invention are purely exemplary and given as an additionaldescription of the present invention determined by the appended claims.

Advantageous Effects

According to the present invention, a method for configuring a controlsignal to effectively support uplink multi-antenna transmission can beprovided. More specifically, a method for indicating whether an uplinkTB is disabled by control information that schedules uplinkmulti-antenna transmission and a method for representing precodinginformation for use in uplink multi-antenna transmission can beprovided.

It will be appreciated by persons skilled in the art that the effectsthat can be achieved with the present invention are not limited to whathas been particularly described hereinabove and other advantages of thepresent invention will be more clearly understood from the followingdetailed description taken in conjunction with the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this application, illustrate embodiments of the invention andtogether with the description serve to explain the principle of theinvention. In the drawings:

FIG. 1 illustrates the structure of a radio frame in a 3^(rd) GenerationPartnership Project Long Term Evolution (3GPP LTE) system;

FIG. 2 illustrates the structure of a downlink resource grid for theduration of one downlink slot;

FIG. 3 illustrates the structure of a downlink subframe;

FIG. 4 illustrates the structure of an uplink subframe;

FIG. 5 is a block diagram of a Single Carrier-Frequency DivisionMultiple Access (SC-FDMA) transmitter;

FIG. 6 illustrates methods for mapping signals output from a DiscreteFrequency Transform (DFT) module illustrated in FIG. 5 to a frequencyarea;

FIG. 7 is a block diagram illustrating DeModulation Reference Signal(DM-RS) transmission in case of SC-FDMA transmission;

FIG. 8 illustrates the positions of symbols to which RSs are mapped inan SC-FDMA subframe structure;

FIG. 9 illustrates a clustered Discrete FrequencyTransform-spread-Orthogonal Frequency Division Multiple Access(DFT-s-OFDMA) scheme in a single carrier system;

FIGS. 10, 11 and 12 illustrate clustered DFT-s-OFDMA schemes in amulti-carrier system;

FIG. 13 illustrates a Multiple Input Multiple Output (MIMO) transmissionscheme;

FIG. 14 is a block diagram of a DFT-s-OFDMA uplink transmissionstructure;

FIGS. 15( a) and 15(b) are block diagrams of structures using layershifting for DFT-s-OFDMA uplink transmission;

FIG. 16 is a flowchart illustrating a method for providing controlinformation that schedules uplink multi-antenna transmission accordingto an embodiment of the present invention;

FIG. 17 is a flowchart illustrating a method for providing controlinformation that schedules uplink multi-antenna transmission accordingto another embodiment of the present invention; and

FIG. 18 is a block diagram of an evolved Node B (eNB) and a UserEquipment (UE) according to the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

The embodiments of the present invention described hereinbelow arecombinations of elements and features of the present invention. Theelements or features may be considered selective unless otherwisementioned. Each element or feature may be practiced without beingcombined with other elements or features. Further, an embodiment of thepresent invention may be constructed by combining parts of the elementsand/or features. Operation orders described in embodiments of thepresent invention may be rearranged. Some constructions of any oneembodiment may be included in another embodiment and may be replacedwith corresponding constructions of another embodiment.

In the embodiments of the present invention, a description is made,centering on a data transmission and reception relationship between aBase Station (BS) and a User Equipment (UE). The BS is a terminal nodeof a network, which communicates directly with a UE. In some cases, aspecific operation described as performed by the BS may be performed byan upper node of the BS.

Namely, it is apparent that, in a network comprised of a plurality ofnetwork nodes including a BS, various operations performed forcommunication with a UE may be performed by the BS, or network nodesother than the BS. The term ‘BS’ may be replaced with the term ‘fixedstation’, ‘Node B’, ‘evolved Node B (eNode B or eNB)’, ‘Access Point(AP)’, etc. The term ‘terminal’ may be replaced with the term ‘UE’,‘Mobile Station (MS)’, ‘Mobile Subscriber Station (MSS)’, ‘SubscriberStation (SS)’, etc.

Specific terms used for the embodiments of the present invention areprovided to help the understanding of the present invention. Thesespecific terms may be replaced with other terms within the scope andspirit of the present invention.

In some cases, to prevent the concept of the present invention frombeing ambiguous, structures and apparatuses of the known art will beomitted, or will be shown in the form of a block diagram based on mainfunctions of each structure and apparatus. Also, wherever possible, thesame reference numbers will be used throughout the drawings and thespecification to refer to the same or like parts.

The embodiments of the present invention can be supported by standarddocuments disclosed for at least one of wireless access systems,Institute of Electrical and Electronics Engineers (IEEE) 802, 3^(rd)Generation Partnership Project (3GPP), 3GPP Long Term Evolution (3GPPLTE), LTE-Advanced (LTE-A), and 3GPP2. Steps or parts that are notdescribed to clarify the technical features of the present invention canbe supported by those documents. Further, all terms as set forth hereincan be explained by the standard documents.

Techniques described herein can be used in various wireless accesssystems such as Code Division Multiple Access (CDMA), Frequency DivisionMultiple Access (FDMA), Time Division Multiple Access (TDMA), OrthogonalFrequency Division Multiple Access (OFDMA), Single Carrier-FrequencyDivision Multiple Access (SC-FDMA), etc. CDMA may be implemented as aradio technology such as Universal Terrestrial Radio Access (UTRA) orCDMA2000. TDMA may be implemented as a radio technology such as GlobalSystem for Mobile communications (GSM)/General Packet Radio Service(GPRS)/Enhanced Data Rates for GSM Evolution (EDGE). OFDMA may beimplemented as a radio technology such as IEEE 802.11 (Wi-Fi), IEEE802.16 (WiMAX), IEEE 802.20, Evolved-UTRA (E-UTRA) etc. UTRA is a partof Universal Mobile Telecommunication System (UMTS). 3GPP LTE is a partof Evolved UMTS (E-UMTS) using E-UTRA. 3GPP LTE employs OFDMA fordownlink and SC-FDMA for uplink. LTE-A is an evolution of 3GPP LTE.WiMAX can be described by the IEEE 802.16e standard (WirelessMetropolitan Area Network (WirelessMAN)-OFDMA Reference System) and theIEEE 802.16m standard (WirelessMAN-OFDMA Advanced System). For clarity,this application focuses on the 3GPP LTE/LTE-A system. However, thetechnical features of the present invention are not limited thereto. Forexample, the technical features of the present invention are applicableto Orthogonal Frequency Division Multiplexing (OFDM) mobilecommunication systems (e.g. an IEEE 802.16m or 802.16x system) otherthan LET-A.

FIG. 1 illustrates a radio frame structure in the 3GPP LTE system. Aradio frame is divided into 10 subframes. Each subframe is furtherdivided into two slots in the time domain. A unit time during which onesubframe is transmitted is defined as a Transmission Time Interval(TTI). For example, one subframe may be 1 ms in duration and one slotmay be 0.5 ms in duration. A slot may include a plurality of OFDMsymbols in the time domain. Because the 3GPP LTE system adopts OFDMA fordownlink, an OFDM symbol represents one symbol period. A symbol may bereferred to as an SC-FDMA symbol or symbol period on the uplink. AResource Block (RB) is a resource allocation unit including a pluralityof contiguous subcarriers in a slot. This radio frame structure ispurely exemplary and thus the number of subframes in a radio frame, thenumber of slots in a subframe, or the number of OFDM symbols in a slotmay vary.

FIG. 2 illustrates the structure of a downlink resource grid for theduration of one downlink slot. A downlink slot includes 7 OFDM symbolsin the time domain and an RB includes 12 subcarriers in the frequencydomain, which does not limit the scope and spirit of the presentinvention. For example, a downlink slot includes 7 OFDM symbols in caseof a normal Cyclic Prefix (CP), whereas a downlink slot includes 6 OFDMsymbols in case of an extended CP. Each element of the resource grid isreferred to as a Resource Element (RE). An RB includes 12×7 REs. Thenumber of RBs in a downlink slot, N^(DL) depends on a downlinktransmission bandwidth. An uplink slot may have the same structure as adownlink slot.

FIG. 3 illustrates a downlink subframe structure. Up to three OFDMsymbols at the start of the first slot in a downlink subframe are usedfor a control region to which control channels are allocated and theother OFDM symbols of the downlink subframe are used for a data regionto which a Physical Downlink Shared Channel (PDSCH) is allocated.Downlink control channels used in the 3GPP LTE system include a PhysicalControl Format Indicator Channel (PCFICH), a Physical Downlink ControlChannel (PDCCH), and a Physical Hybrid automatic repeat request (HARQ)Indicator Channel (PHICH). The PCFICH is located in the first OFDMsymbol of a subframe, carrying information about the number of OFDMsymbols used for transmission of control channels in the subframe. ThePHICH delivers an HARQ ACKnowledgment/Negative ACKnowledgment (ACK/NACK)signal in response to an uplink transmission. Control informationcarried on the PDCCH is called Downlink Control Information (DCI). TheDCI transports uplink or downlink scheduling information, or uplinktransmission power control commands for UE groups. The PDCCH deliversinformation about resource allocation and a transport format for aDownlink Shared Channel (DL-SCH), resource allocation information aboutan Uplink Shared Channel (UL-SCH), paging information of a PagingChannel (PCH), system information on the DL-SCH, information aboutresource allocation for a higher-layer control message such as a RandomAccess Response transmitted on the PDSCH, a set of transmission powercontrol commands for individual UEs of a UE group, transmission powercontrol information, Voice Over Internet Protocol (VoIP) activationinformation, etc. A plurality of PDCCHs may be transmitted in thecontrol region. A UE may monitor a plurality of PDCCHs. A PDCCH isformed by aggregation of one or more consecutive Control ChannelElements (CCEs). A CCE is a logical allocation unit used to provide aPDCCH at a coding rate based on the state of a radio channel. A CCEincludes a plurality of RE groups. The format of a PDCCH and the numberof available bits for the PDCCH are determined according to thecorrelation between the number of CCEs and a coding rate provided by theCCEs. An eNB determines the PDCCH format according to DCI transmitted toa UE and adds a Cyclic Redundancy Check (CRC) to control information.The CRC is masked by an Identifier (ID) known as a Radio NetworkTemporary Identifier (RNTI) according to the owner or usage of thePDCCH. If the PDCCH is directed to a specific UE, its CRC may be maskedby a cell-RNTI (C-RNTI) of the UE. If the PDCCH carries a pagingmessage, the CRC of the PDCCH may be masked by a Paging IndicatorIdentifier (P-RNTI). If the PDCCH carries system information,particularly, a System Information Block (SIB), its CRC may be masked bya system information ID and a System Information RNTI (SI-RNTI). Toindicate that the PDCCH carries a Random Access Response in response toa Random Access Preamble transmitted by a UE, its CRC may be masked by aRandom Access-RNTI (RA-RNTI).

FIG. 4 illustrates an uplink subframe structure. An uplink subframe maybe divided into a control region and a data region in the frequencydomain. A Physical Uplink Control Channel (PUCCH) carrying uplinkcontrol information is allocated to the control region and a PhysicalUplink Shared Channel (PUSCH) carrying user data is allocated to thedata region. To maintain a single carrier property, a UE does nottransmit a PUSCH and a PUCCH simultaneously. A PUCCH for a UE isallocated to an RB pair in a subframe. The RBs of the RB pair occupydifferent subcarriers in two slots. Thus it is said that the RB pairallocated to the PUCCH is frequency-hopped over a slot boundary.

Uplink Multiple Access Schemes

A description will be given below of uplink multiple access schemes.

First of all, an SC-FDMA transmission scheme will be described. SC-FDMAis also called DFT-s-OFDMA, different from later-described clusteredDFT-s-OFDMA.

SC-FDMA is a transmission scheme that keeps a Peak-to-Average PowerRatio (PARP) or Cube Metric (CM) value low and efficiently transmits asignal, avoiding the non-linear distortion area of a power amplifier.PAPR is a parameter representing waveform characteristics, computed bydividing the peak amplitude of a waveform by a time-averaged Root MeanSquare (RMS) value. CM is another parameter representing a value thatPAPR represents. PAPR is associated with a dynamic range that a poweramplifier should support in a transmitter. That is, to support ahigh-PAPR transmission scheme, the dynamic range (or linear area) of thepower amplifier needs to be wide. As a power amplifier has a widerdynamic range, it is more expensive. Therefore, a transmission schemethat maintains a PAPR value low is favorable for uplink transmission. Inthis context, due to the advantage of low PAPR, SC-FDMA is employed asan uplink transmission scheme in the current 3GPP LTE system.

FIG. 5 is a block diagram of an SC-FDMA transmitter.

A serial-to-parallel converter 501 converts one block of N symbols inputto the transmitter to parallel signals. An N-point DFT module 502spreads the parallel signals and a subcarrier mapping module 503 mapsthe spread parallel signals to a frequency area. Each subcarrier signalis a linear combination of N symbols. An M-point Inverse Fast FourierTransform (IFFT) module 504 converts the mapped frequency signals totime signals. A parallel-to-serial converter 505 converts the timesignals to a serial signal and adds a CP to the serial signal. The DFTprocessing of the N-point DFT module 502 compensates for the effects ofthe IFFT processing of the M-point IFFT module 504 to a certain degree.The signals input to the DFT module 502 have a low PAPR which isincreased after the DFT processing. The IFFT signals output from theIFFT module 504 may have a low PAPR again.

FIG. 6 illustrates methods for mapping signals output from the DFTmodule 502 to a frequency area. A signal output from the SC-FDMAtransmitter may satisfy the single carrier property by performing one oftwo mapping schemes illustrated in FIG. 6. FIG. 6( a) illustrates alocalized mapping scheme in which the signals output from the DFT module502 are mapped only to a specific part of a subcarrier area. FIG. 6( b)illustrates a distributed mapping scheme in which the signals outputfrom the DFT module 502 are distributed across a total subcarrier area.The legacy 3GPP LTE standard (e.g. release 8) uses localized mapping.

FIG. 7 is a block diagram illustrating transmission of a Referencesignal (RS) for use in demodulating a signal transmitted in SC-FDMA.According to the legacy 3GPP LTE standard (e.g. release 8), while a timesignal of data is converted to a frequency signal by DFT, mapped tosubcarriers, IFFT-processed, and then transmitted (refer to FIG. 5), anRS is generated directly in the frequency domain without DFT processing(701), mapped to subcarriers (702), IFFT-processed (703), attached witha CP, and then transmitted.

FIG. 8 illustrates the positions of symbols to which RSs are mapped inan SC-FDMA subframe structure. FIG. 8( a) illustrates a case where an RSis positioned in the 4^(th) SC-FDMA symbol of each of two slots in asubframe, when a normal CP is used. FIG. 8( b) illustrates a case wherean RS is positioned in the 3^(rd) SC-FDMA symbol of each of two slots ina subframe, when an extended CP is used.

With reference to FIGS. 9 to 12, clustered DFT-s-OFDMA will bedescribed. Clustered DFT-s-OFDMA is a modification to theabove-described SC-FDMA, in which a DFT signal is divided into aplurality of sub-blocks and mapped to positions apart from each other inthe frequency domain.

FIG. 9 illustrates a clustered DFT-s-OFDMA scheme in a single carriersystem. For example, a DFT output may be divided in Nsb sub-blocks(sub-block #0 to sub-block #Nsb-1). The sub-blocks, sub-block #0 tosub-block #Nsb-1 are mapped to positions spaced from each other in thefrequency domain on a single carrier (e.g. a carrier having a bandwidthof 20 MHz). Each sub-block may be mapped to a frequency area in thelocalized mapping scheme.

FIGS. 10 and 11 illustrate clustered DFT-s-OFDMA schemes in amulti-carrier system.

FIG. 10 illustrates an example of generating a signal through one IFFTmodule, when multiple carriers are contiguously configured (i.e. therespective frequency bands of the multiple carriers are contiguous) anda specific subcarrier spacing is aligned between adjacent carriers. Forexample, a DFT output may be divided into Nsb sub-blocks (sub-block #0to sub-block #Nsb-1) and the sub-blocks, sub-block #0 to sub-block#Nsb-1 may be mapped, in a one-to-one correspondence, to the ComponentCarriers (CCs), CC #0 to CC #Nsb-1 (each CC may have, for example, abandwidth of 20 MHz). Each sub-block may be mapped to a frequency areain the localized mapping scheme. The sub-blocks mapped to the respectiveCCs may be converted to a time signal through a single IFFT module.

FIG. 11 illustrates an example of generating signals through a pluralityof IFFT modules, when multiple carriers are non-contiguously configured(i.e. the respective frequency bands of the multiple carriers arenon-contiguous). For example, a DFT output may be divided into Nsbsub-blocks, sub-block #0 to sub-block #Nsb-1 and the sub-blocks,sub-block #0 to sub-block #Nsb-1 may be mapped, in a one-to-onecorrespondence, to the CCs, CC #0 to CC #Nsb-1 (each CC may have, forexample, a bandwidth of 20 MHz). Each sub-block may be mapped to afrequency area in the localized mapping scheme. The sub-blocks mapped tothe respective CCs may be converted to time signals through respectiveIFFT modules.

If the clustered DFT-s-OFDMA scheme for a single carrier illustrated inFIG. 9 is intra-carrier DFT-s-OFDMA, it may be said that the clusteredDFT-s-OFDMA schemes for multiple carriers illustrated in FIGS. 10 and 11are inter-carrier DFT-s-OFDMA. Intra-carrier DFT-s-OFDMA andinter-carrier DFT-s-OFDMA may be used in combination.

FIG. 12 illustrates a chunk-specific DFT-s-OFDMA scheme in which DFT,frequency mapping, and IFFT are performed on a chunk basis.Chunk-specific DFT-s-OFDMA may also be referred to as Nx SC-FDMA. A codeblock resulting from code block segmentation is divided into chunks andthe chunks are channel-encoded and modulated individually. The modulatedsignals are subjected to DFT, frequency mapping, and IFFT and the IFFTsignals are summed and then added with a CP in the same manner asdescribed with reference to FIG. 5. The Nx SC-FDMA scheme illustrated inFIG. 12 is applicable to both a case of contiguous multiple carriers anda case of non-contiguous multiple carriers.

MIMO System

MIMO does not depend on a single antenna path to receive a wholemessage. Rather, it completes the message by combining data fragmentsreceived through a plurality of antennas. Because MIMO can increase datarate within a certain area or extend system coverage at a given datarate, it is considered as a promising future-generation mobilecommunication technology that may find its use in a wide range includingmobile terminals, relays, etc. MIMO can overcome a limited transmissioncapacity caused by increased data communication.

MIMO schemes can be categorized into spatial multiplexing and spatialdiversity depending on whether the same data is transmitted or not. Inspatial multiplexing, different data is transmitted simultaneouslythrough a plurality of Tx antennas. As a transmitter transmits differentdata through different Tx antennas and a receiver distinguishes thetransmission data by appropriate interference cancellation and signalprocessing, a transmission rate can be increased by as much as thenumber of transmission antennas. Spatial diversity is a scheme thatachieves transmit diversity by transmitting the same data through aplurality of Tx antennas. Space time channel coding is an example ofspatial diversity. Since the same data is transmitted through aplurality of Tx antennas, spatial diversity can maximize a transmissiondiversity gain (a performance gain). However, spatial diversity does notincrease transmission rate. Rather, it increases transmissionreliability using a diversity gain. These two schemes may offer theirbenefits when they are appropriately used in combination. In addition,MIMO schemes may be categorized into open-loop MIMO (orchannel-independent MIMO) and closed-loop MIMO (or channel-dependentMIMO) depending on whether a receiver feeds back channel information toa transmitter.

FIG. 13 illustrates the configuration of a typical MIMO communicationsystem. Referring to FIG. 13( a), when both the number of Tx antennasand the number of Rx antennas respectively to N_(T) and N_(R), atheoretical channel transmission capacity is increased, compared to useof a plurality of antennas at only one of a transmitter and a receiver.The channel transmission capacity is increased in proportion to thenumber of antennas. Therefore, transmission rate and frequencyefficiency can be increased remarkably. Given a maximum transmissionrate R_(o) that may be achieved with a single antenna, the transmissionrate may be increased, in theory, to the product of R_(o) and atransmission rate increase rate R_(i) illustrated in Equation 1 due toan increase in channel transmission capacity in case of multipleantennas.

R _(i)=min(N _(T) ,N _(R))  Equation 1

For instance, a MIMO communication system with 4 Tx antennas and 4 Rxantennas may achieve a four-fold increase in transmission ratetheoretically, relative to a single-antenna system.

Communication in a MIMO system will be described in detail throughmathematical modeling. As illustrated in FIG. 13( a), it is assumed thatN_(T) Tx antennas and N_(R) Rx antennas exist. Regarding a transmissionsignal, up to N_(T) pieces of information can be transmitted through theN_(T) Tx antennas, as expressed as the following vector.

s=[s ₁ ,s ₂ , . . . ,s _(N) _(T) ]^(T)  Equation 2

A different transmission power may be applied to each piece oftransmission information, s₁, s₂, . . . , s_(N) _(T) . Let thetransmission power levels of the transmission information be denoted byP₁, P₂, . . . , P_(N) _(T) , respectively. Then the transmissionpower-controlled transmission information vector is given as

ŝ=└ŝ ₁ ,ŝ ₂ , . . . ,ŝ _(N) _(T) ┘^(T) =[Ps ₁ ,Ps ₂ , . . . ,Ps _(N)_(T) ]^(T)  Equation 3

The transmission power-controlled transmission information vector ŝ maybe expressed as follows, using a diagonal matrix P of transmissionpower.

$\begin{matrix}{\hat{s} = {{\begin{bmatrix}P_{1} & \; & \; & 0 \\\; & P_{2} & \; & \; \\\; & \; & \ddots & \; \\0 & \; & \; & P_{N_{T}}\end{bmatrix}\begin{bmatrix}s_{1} \\s_{2} \\\vdots \\s_{N_{T}}\end{bmatrix}} = {Ps}}} & {{Equation}\mspace{14mu} 4}\end{matrix}$

N_(T) transmission signals x₁, x₂, . . . , x_(N) _(T) may be generatedby multiplying the transmission power-controlled information vector ŝ bya weight matrix W. The weight matrix W functions to appropriatelydistribute the transmission information to the Tx antennas according totransmission channel states, etc. These N_(T) transmission signals x₁,x₂, . . . x_(N) _(T) are represented as a vector X, which may bedetermined by Equation 5. Herein, w_(ij) denotes a weight between ani^(th) Tx antenna and a j^(th) piece of information. W is called aweight matrix or a precoding matrix.

$\begin{matrix}\begin{matrix}{X = \begin{bmatrix}x_{1} \\x_{2} \\\vdots \\x_{i} \\\vdots \\x_{N_{T}}\end{bmatrix}} \\{= {\begin{bmatrix}w_{11} & w_{12} & \ldots & w_{1\; N_{T}} \\w_{12} & w_{12} & \ldots & w_{2\; N_{T}} \\\vdots & \; & \ddots & \; \\w_{i\; 2} & w_{i\; 2} & \ldots & w_{i\; N_{T}} \\\vdots & \; & \ddots & \; \\w_{N_{T}1} & w_{N_{T}2} & \ldots & w_{N_{T}N_{T}}\end{bmatrix}\begin{bmatrix}{\hat{s}}_{1} \\{\hat{s}}_{2} \\\vdots \\{\hat{s}}_{j} \\\vdots \\{\hat{s}}_{N_{T}}\end{bmatrix}}} \\{= {W\; \hat{s}}} \\{= {WPs}}\end{matrix} & {{Equation}\mspace{14mu} 5}\end{matrix}$

Given N_(R) Rx antennas, signals received at the respective Rx antennas,y₁, y₂, . . . , y_(N) _(R) may be represented as the following vector.

y=[y ₁ ,y ₂ , . . . ,y _(N) _(R) ]^(T)  Equation 6

When channels are modeled in the MIMO communication system, they may bedistinguished according to the indexes of Tx and Rx antennas and thechannel between a j^(th) Tx antenna and an i^(th) Rx antenna may berepresented as h_(ij). It is to be noted herein that the index of the Rxantenna precedes that of the Tx antenna in h_(ij).

The channels may be represented as vectors and matrices by groupingthem. The vector representation of channels may be carried out in thefollowing manner. FIG. 13( b) illustrates channels from N_(T) Txantennas to an i^(th) Rx antenna.

As illustrated in FIG. 13( b), channels from the N_(T) Tx antennas to ani^(th) Rx antenna may be expressed as

h _(i) ^(T) =[h _(i1) ,h _(i2) , . . . ,h _(iN) _(T) ]  Equation 7

Also, all channels from the N_(T) Tx antennas to the N_(R) Rx antennasmay be expressed as the following matrix.

$\begin{matrix}\begin{matrix}{H = \begin{bmatrix}h_{1}^{T} \\h_{2}^{T} \\\vdots \\h_{i}^{T} \\\vdots \\h_{N_{R}}^{T}\end{bmatrix}} \\{= \begin{bmatrix}h_{11} & h_{12} & \ldots & h_{1\; N_{T}} \\h_{12} & h_{12} & \ldots & h_{2\; N_{T}} \\\vdots & \; & \ddots & \; \\h_{i\; 2} & h_{i\; 2} & \ldots & h_{i\; N_{T}} \\\vdots & \; & \ddots & \; \\h_{N_{R}1} & h_{N_{R}2} & \ldots & h_{N_{R}N_{T}}\end{bmatrix}}\end{matrix} & {{Equation}\mspace{14mu} 8}\end{matrix}$

Actual channels experience the above channel matrix H and then are addedwith Additive White Gaussian Noise (AWGN). The AWGN n₁, n₂, . . . ,n_(N) _(R) added to the N_(R) Rx antennas is given as the followingvector.

n=[n ₁ ,n ₂ , . . . ,n _(N) _(R) ]^(T)  Equation 9

From the above modeled equations, the received signal is given as

$\begin{matrix}\begin{matrix}{y = \begin{bmatrix}y_{1} \\y_{2} \\\vdots \\y_{i} \\\vdots \\y_{N_{R}}\end{bmatrix}} \\{= {{\begin{bmatrix}h_{11} & h_{12} & \ldots & h_{1\; N_{T}} \\h_{12} & h_{12} & \ldots & h_{2\; N_{T}} \\\vdots & \; & \ddots & \; \\h_{i\; 2} & h_{i\; 2} & \ldots & h_{i\; N_{T}} \\\vdots & \; & \ddots & \; \\h_{N_{R}1} & h_{N_{R}2} & \ldots & h_{N_{R}N_{T}}\end{bmatrix}\begin{bmatrix}x_{1} \\x_{2} \\\vdots \\x_{j} \\\vdots \\x_{N_{T}}\end{bmatrix}} + \begin{bmatrix}n_{1} \\n_{2} \\\vdots \\n_{i} \\\vdots \\n_{N_{R}}\end{bmatrix}}} \\{= {{Hx} + n}}\end{matrix} & {{Equation}\mspace{14mu} 10}\end{matrix}$

In the meantime, the numbers of rows and columns in the channel matrix Hrepresenting channel states are determined according to the numbers ofTx and Rx antennas. The number of rows is identical to that of Rxantennas, N_(R) and the number of columns is identical to that of Txantennas, N_(T). Thus, the channel matrix H is of size N_(R)×N_(T). Ingeneral, the rank of a matrix is defined as the smaller between thenumbers of independent rows and columns. Accordingly, the rank of thematrix is not larger than the number of rows or columns. For example,the rank of the matrix H, rank(H) is limited as follows.

rank(H)≦min(N _(T) ,N _(R))  Equation 11

In relation to the afore-described MIMO transmission schemes, acodebook-based precoding scheme will be described in great detail.

In the codebook-based precoding scheme, a transmitter and a receivershare a codebook including a predetermined number of precoding matricesaccording to a transmission rank, the number of antennas, etc. That is,if feedback information is finite, the precoding-based codebook schememay be used. The receiver may measure channel states from receivedsignals and feedback information about a finite number of preferredprecoding matrices (i.e. the indexes of the precoding matrices) based onthe afore-described codebook information. For example, the receiver maymeasure a received signal by Maximum Likelihood (ML) or Minimum MeansSquare Error (MMSE) and may select an optimum precoding matrix. Thereceiver may transmit precoding matrix information for each codeword tothe transmitter, which should not be construed as limiting the presentinvention.

Upon receipt of feedback information from the receiver, the transmittermay select a specific precoding matrix from a codebook based on thereceived information. After selecting the precoding matrix, thetransmitter may precode a transmission signal by multiplying as manylayer signals as a transmission rank by the selected precoding matrixand may transmit the precoded transmission signal through a plurality ofantennas. The number of rows is equal to the number of antennas and thenumber of columns is equal to the rank in the precoding matrix. Forexample, if the number of Tx antennas is 4 and the number of layers is2, the precoding matrix may be a 4×2 matrix. The following Equation 12describes mapping of information mapped to layers to antennas by aprecoding matrix.

$\begin{matrix}{\begin{bmatrix}y_{1} \\y_{2} \\y_{3} \\y_{4}\end{bmatrix} = {\begin{bmatrix}p_{11} & p_{21} \\p_{12} & p_{22} \\p_{13} & p_{23} \\p_{14} & p_{34}\end{bmatrix} \cdot \begin{bmatrix}x_{1} \\x_{2}\end{bmatrix}}} & {{Equation}\mspace{14mu} 12}\end{matrix}$

Referring to Equation 12, x₁ and x₂ denote information mapped to layersand each element of the 4×2 matrix, p_(ij) denotes a weight used forprecoding. y₁, y₂, y₃ and y₄ denote information mapped to the antennas,which may be transmitted through the respective antennas in OFDM.

Upon receipt of the precoded signal from the transmitter, the receivermay recover the received signal by reversely performing the precoding ofthe transmitter. In general, a precoding matrix satisfies a unitarymatrix U condition such as U*U^(H)=I. The reverse operation of precodingmay be performed by multiplying a received signal by the Hermitianmatrix P^(H) of a precoding matrix used in precoding of the transmitter.

As described before, the 3GPP LTE-A (LTE Release-10) system may adoptuplink multi-antenna transmission in order to increase uplinktransmission throughput. As an uplink multi-antenna transmission scheme,a multi-transmission stream or multi-transmission layer transmissionscheme may be used for a single UE for the purpose of spatialmultiplexing. This is called SU-MIMO. In uplink SU-MIMO, link adaptationmay be applied to each individual transmission stream or transmissionstream group. Different Modulation and Coding Schemes (MCSs) may be usedfor link adaptation. For this purpose, Multiple CodeWord (MCW)-basedtransmission may be performed on uplink.

In an MCW MIMO scheme, for example, up to two CodeWords (CWs) may betransmitted simultaneously. For the MIMO transmission, information aboutan MCS used in a transmitter, a New Data Indicator (NDI) indicatingwhether transmitted data is new data or retransmission data, and aRedundancy Version (RV) indicating a transmitted sub-packet in case ofretransmission is needed. An MCS, NDI, and RV may be defined for eachTransport Block (TB).

A plurality of TBs may be mapped to a plurality of CWs according to atransport block-to-codeword mapping rule. For example, let two RBs bedenoted by TB1 and TB2 and let two CWs be denoted by CW0 and CW1. Whenthe two TBs TB1 and TB2 are enabled, the first and second TBs TB1 andTB2 may be mapped respectively to the first and second CWs CW0 and CW1.Or the first TB TB1 may be mapped to the second CW CW1 and the second TBTB2 may be mapped to the first CW CW0 according to the value of atransport block-to-codeword swap flag. If one of the two TBs is enabledand the other TB is disabled, the enabled TB may be mapped to the firstCW CW0. That is, a one-to-one mapping relationship is placed between TBsand CWs. TB disabling covers the size of a TB being 0. When the size ofa TB is 0, the TB is not mapped to a CW.

FIG. 14 is a block diagram of an uplink MCW SU-MIMO transmissionstructure.

After encoding in encoders, one or more CWs may be scrambled with aUE-specific scrambling signal. The scrambled CWs are modulated tocomplex symbols in Binary Phase Shift Keying (BPSK), Quadrature PhaseShift Keying (QPSK), 16-ary Quadrature Amplitude Modulation (16QAM), or64-ary QAM (64QAM) according to the type of a transmission signal and/ora channel state. The modulated complex symbols are mapped to one or morelayers. In case of signal transmission through a single antenna, one CWis mapped to one layer and then transmitted. In contrast, in case ofsignal transmission through multiple antennas, a codeword-to-layermapping relationship may be established according to a transmissionscheme as illustrated in [Table 1] and [Table 2].

TABLE 1 Number of Number of Codeword-to-layer mapping layers code wordsi = 0.1, . . . , M_(symb) ^(layer) − 1 1 1 x⁽⁰⁾(i) = d⁽⁰⁾(i) M_(symb)^(layer) = M_(symb) ⁽⁰⁾ 2 2 x⁽⁰⁾(i) = d⁽⁰⁾(i) M_(symb) ^(layer) =M_(symb) ⁽⁰⁾ = M_(symb) ⁽¹⁾ x⁽¹⁾(i) = d⁽¹⁾(i) 2 1 x⁽⁰⁾(i) = d⁽⁰⁾(2i)M_(symb) ^(layer) = M_(symb) ⁽⁰⁾/2 x⁽¹⁾(i) = d⁽⁰⁾(2i +1) 3 2 x⁽⁰⁾(i) =d⁽⁰⁾(i) M_(symb) ^(layer) = M_(symb) ⁽⁰⁾ = M_(symb) ⁽¹⁾/2 x⁽¹⁾(i) =d⁽¹⁾(2i) x⁽²⁾(i) = d⁽¹⁾(2i + 1) 4 2 x⁽⁰⁾(i) = d⁽⁰⁾(2i) M_(symb) ^(layer)= M_(symb) ⁽⁰⁾/2 = M_(symb) ⁽¹⁾/2 x⁽¹⁾(i) = d⁽⁰⁾(2i + 1) x⁽²⁾(i) =d⁽¹⁾(2i) x⁽³⁾(i) = d⁽¹⁾(2i + 1)

TABLE 2 Number Number of Codeword-to-layer mapping of layers code wordsi = 0, 1, . . . , M_(symb) ^(layer) −1 2 1 x⁽⁰⁾ (i) = d⁽⁰⁾ (2i) M_(symb)^(layer) = M_(symb) ⁽⁰⁾/2 x⁽¹⁾ (i) = d⁽⁰⁾ (2i + 1) 4 1 x⁽⁰⁾ (i) = d⁽⁰⁾(2i) x⁽¹⁾ (i) = d⁽⁰⁾ (4i + 1) x⁽²⁾ (i) = d⁽⁰⁾ (4i + 2) x⁽³⁾ (i) = d⁽⁰⁾(4i + 3) $\begin{matrix}{M_{symb}^{layer} = \{ {\begin{matrix}{M_{symb}^{(0)}/4} \\{( {M_{symb}^{(0)} + 2} )/4}\end{matrix}\begin{matrix}{{{if}\mspace{14mu} M_{symb}^{(0)}\mspace{14mu} {mod}\mspace{14mu} 4} = 0} \\{{{if}\mspace{14mu} M_{symb}^{(0)}\mspace{14mu} {mod}\mspace{14mu} 4} \neq 0}\end{matrix}} } \\\begin{matrix}{{{If}\mspace{14mu} M_{symb}^{(0)}\mspace{14mu} {mod}\mspace{14mu} 4} \neq {0\mspace{14mu} {two}\mspace{14mu} {null}\mspace{14mu} {symbols}\mspace{14mu} {shall}\mspace{14mu} {be}}} \\{{appended}\mspace{14mu} {to}\mspace{14mu} d^{(0)}\mspace{14mu} ( {M_{symb}^{(0)} - 1} )}\end{matrix}\end{matrix}$

[Table 1] illustrates an example of transmitting a signal in spatialmultiplexing and [Table 2] illustrates an example of transmitting asignal in transmit diversity. In [Table 1] and [Table 2], x^((a))(i)denotes an i^(th) symbol of a layer with index a and d^((a))(i) denotesan i^(th) symbol of a CW with index a. A mapping relationship betweenthe number of CWs and the number of layers used for transmission may beknown from “Number of layers” and “Number of codewords” in [Table 1] and[Table 2]. “Codeword-to-Layer mapping” indicates how the symbols of eachCW are mapped to a layer.

As noted from [Table 1] and [Table 2], although one CW may be mapped toone layer on a symbol basis prior to transmission, one CW may bedistributed to up to 4 layers as in the second case of [Table 2]. Whenone CW is distributed to a plurality of layers in this manner, thesymbols of each CW are mapped sequentially to layers. On the other hand,in case of single CW transmission, a single encoder and a singlemodulation block exist.

The layer-mapped signals may be subject to DFT. In addition, thelayer-mapped signals may be multiplied by a specific precoding matrixselected according to a channel state and then assigned to Tx antennas.To avoid an increase in PAPR (or CM) of an uplink transmission from aUE, precoding may be performed in the frequency domain after DFT in theDFT-s-OFDMA structure.

The antenna-specific transmission signals may be mapped totime-frequency REs for transmission and transmitted through the antennasafter being processed in OFDM signal generators.

FIG. 15 is exemplary block diagrams of layer shifting in an uplink MCWSU MIMO transmission structure.

Layer shifting (or layer permutation) refers to permuting the order ofmapping transmission streams or transmission layers on a time resourcearea unit (e.g. on an OFDM symbol basis or on a slot basis). Layershifting may be performed before DFT (FIG. 15( a)) or after DFT (FIG.15( b)). Or layer shifting may take place after OFDM signal generation.However, layer shifting is not always needed and thus may be excludedfrom uplink transmission.

Precoding will be described in greater detail in relation to FIGS. 14and 15. Precoding is a process of combining a transmission signal with aweight vector or a weight matrix to transmit a signal on spatialchannels. The precoding blocks of FIGS. 14 and 15 may implement transmitdiversity, long-term beamforming, precoded signal multiplexing, etc. Toeffectively support precoded signal multiplexing, precoding weights maybe constructed into a codebook. [Table 3] to [Table 7] illustrateexemplary codebooks used to prevent an increase in CM for uplinktransmission.

[Table 3] illustrates an exemplary codebook available for uplink spatialmultiplexing transmission through 2 Tx antennas. Given two Tx antennas,one of 6 precoding matrices is available for rank-1 transmission and oneprecoding matrix is available for rank-2 transmission.

TABLE 3 Codebook Number of layers ν Index 1 2 0$\frac{1}{\sqrt{2}}\begin{bmatrix}1 \\1\end{bmatrix}$ $\frac{1}{\sqrt{2}}\lbrack {\begin{matrix}1 \\0\end{matrix}\begin{matrix}0 \\1\end{matrix}} \rbrack$ 1 $\frac{1}{\sqrt{2}}\begin{bmatrix}1 \\{- 1}\end{bmatrix}$ 2 $\frac{1}{\sqrt{2}}\begin{bmatrix}1 \\j\end{bmatrix}$ 3 $\frac{1}{\sqrt{2}}\begin{bmatrix}1 \\{- j}\end{bmatrix}$ — 4 $\frac{1}{\sqrt{2}}\begin{bmatrix}1 \\0\end{bmatrix}$ 5 $\frac{1}{\sqrt{2}}\begin{bmatrix}0 \\1\end{bmatrix}$

[Table 4] illustrates precoding matrices included in a 6-bit precodingcodebook available for transmission of one layer (i.e. rank-1transmission) in uplink spatial multiplexing transmission through 4 Txantennas. For 4-Tx rank-1 transmission, one of a total of 24 precodingmatrices may be used.

TABLE 4 Codebook Index 0 to 7 $\frac{1}{2}\begin{bmatrix}1 \\1 \\1 \\{- 1}\end{bmatrix}$ $\frac{1}{2}\begin{bmatrix}1 \\1 \\j \\j\end{bmatrix}$ $\frac{1}{2}\begin{bmatrix}1 \\1 \\{- 1} \\1\end{bmatrix}$ $\frac{1}{2}\begin{bmatrix}1 \\1 \\{- j} \\{- j}\end{bmatrix}$ $\frac{1}{2}\begin{bmatrix}1 \\j \\1 \\j\end{bmatrix}$ $\frac{1}{2}\begin{bmatrix}1 \\j \\j \\1\end{bmatrix}$ $\frac{1}{2}\begin{bmatrix}1 \\j \\{- 1} \\{- j}\end{bmatrix}$ $\frac{1}{2}\begin{bmatrix}1 \\j \\{- j} \\{- 1}\end{bmatrix}$ Index  8 to 15 $\frac{1}{2}\begin{bmatrix}1 \\{- 1} \\1 \\1\end{bmatrix}$ $\frac{1}{2}\begin{bmatrix}1 \\{- 1} \\j \\{- j}\end{bmatrix}$ $\frac{1}{2}\begin{bmatrix}1 \\{- 1} \\{- 1} \\{- 1}\end{bmatrix}$ $\frac{1}{2}\begin{bmatrix}1 \\{- 1} \\{- j} \\j\end{bmatrix}$ $\frac{1}{2}\begin{bmatrix}1 \\{- j} \\1 \\{- j}\end{bmatrix}$ $\frac{1}{2}\begin{bmatrix}1 \\{- j} \\j \\{- 1}\end{bmatrix}$ $\frac{1}{2}\begin{bmatrix}1 \\{- j} \\{- 1} \\j\end{bmatrix}$ $\frac{1}{2}\begin{bmatrix}1 \\{- j} \\{- j} \\1\end{bmatrix}$ Index 16 to 23 $\frac{1}{2}\begin{bmatrix}1 \\0 \\1 \\0\end{bmatrix}$ $\frac{1}{2}\begin{bmatrix}1 \\0 \\{- 1} \\0\end{bmatrix}$ $\frac{1}{2}\begin{bmatrix}1 \\0 \\j \\0\end{bmatrix}$ $\frac{1}{2}\begin{bmatrix}1 \\0 \\{- j} \\0\end{bmatrix}$ $\frac{1}{2}\begin{bmatrix}0 \\1 \\0 \\1\end{bmatrix}$ $\frac{1}{2}\begin{bmatrix}0 \\1 \\0 \\{- 1}\end{bmatrix}$ $\frac{1}{2}\begin{bmatrix}0 \\1 \\0 \\j\end{bmatrix}$ $\frac{1}{2}\begin{bmatrix}0 \\1 \\0 \\{- j}\end{bmatrix}$

[Table 5] illustrates precoding matrices included in a precodingcodebook available for transmission of 2 layers (i.e. rank-2transmission) in an uplink spatial multiplexing transmission schemeusing 4 Tx antennas. For 4-Tx rank-2 transmission, one of a total of 16precoding matrices may be used.

TABLE 5 Codebook Index 0 to 3 $\frac{1}{2}\begin{bmatrix}1 & 0 \\1 & 0 \\0 & 1 \\0 & {- j}\end{bmatrix}$ $\frac{1}{2}\begin{bmatrix}1 & 0 \\1 & 0 \\0 & 1 \\0 & j\end{bmatrix}$ $\frac{1}{2}\begin{bmatrix}1 & 0 \\{- j} & 0 \\0 & 1 \\0 & 1\end{bmatrix}$ $\frac{1}{2}\begin{bmatrix}1 & 0 \\{- j} & 0 \\0 & 1 \\0 & {- 1}\end{bmatrix}$ Index 4 to 7 $\frac{1}{2}\begin{bmatrix}1 & 0 \\{- 1} & 0 \\0 & 1 \\0 & {- j}\end{bmatrix}$ $\frac{1}{2}\begin{bmatrix}1 & 0 \\{- 1} & 0 \\0 & 1 \\0 & 1\end{bmatrix}$ $\frac{1}{2}\begin{bmatrix}1 & 0 \\j & 0 \\0 & 1 \\0 & 1\end{bmatrix}$ $\frac{1}{2}\begin{bmatrix}1 & 0 \\j & 0 \\0 & 1 \\0 & {- 1}\end{bmatrix}$ Index  8 to 11 $\frac{1}{2}\begin{bmatrix}1 & 0 \\0 & 1 \\1 & 0 \\0 & 1\end{bmatrix}$ $\frac{1}{2}\begin{bmatrix}1 & 0 \\0 & 1 \\1 & 0 \\0 & {- 1}\end{bmatrix}$ $\frac{1}{2}\begin{bmatrix}1 & 0 \\0 & 1 \\{- 1} & 0 \\0 & 1\end{bmatrix}$ $\frac{1}{2}\begin{bmatrix}1 & 0 \\0 & 1 \\{- 1} & 0 \\0 & {- 1}\end{bmatrix}$ Index 12 to 15 $\frac{1}{2}\begin{bmatrix}1 & 0 \\0 & 1 \\0 & 1 \\1 & 0\end{bmatrix}$ $\frac{1}{2}\begin{bmatrix}1 & 0 \\0 & 1 \\0 & {- 1} \\1 & 0\end{bmatrix}$ $\frac{1}{2}\begin{bmatrix}1 & 0 \\0 & 1 \\0 & 1 \\{- 1} & 0\end{bmatrix}$ $\frac{1}{2}\begin{bmatrix}1 & 0 \\0 & 1 \\0 & {- 1} \\{- 1} & 0\end{bmatrix}$

[Table 6] illustrates precoding matrices included in a precodingcodebook available for transmission of 3 layers (i.e. rank-3transmission) in the uplink spatial multiplexing transmission schemeusing 4 Tx antennas. For 4-Tx rank-3 transmission, one of a total of 12precoding matrices may be used.

TABLE 6 Codebook Index 0 to 3 $\frac{1}{2}\begin{bmatrix}1 & 0 & 0 \\1 & 0 & 0 \\0 & 1 & 0 \\0 & 0 & 1\end{bmatrix}$ $\frac{1}{2}\begin{bmatrix}1 & 0 & 0 \\{- 1} & 0 & 0 \\0 & 1 & 0 \\0 & 0 & 1\end{bmatrix}$ $\frac{1}{2}\begin{bmatrix}1 & 0 & 0 \\0 & 1 & 0 \\1 & 0 & 0 \\0 & 0 & 1\end{bmatrix}$ $\frac{1}{2}\begin{bmatrix}1 & 0 & 0 \\0 & 1 & 0 \\{- 1} & 0 & 0 \\0 & 0 & 1\end{bmatrix}$ Index 4 to 7 $\frac{1}{2}\begin{bmatrix}1 & 0 & 0 \\0 & 1 & 0 \\0 & 0 & 1 \\1 & 0 & 0\end{bmatrix}$ $\frac{1}{2}\begin{bmatrix}1 & 0 & 0 \\0 & 1 & 0 \\0 & 0 & 1 \\{- 1} & 0 & 0\end{bmatrix}$ $\frac{1}{2}\begin{bmatrix}0 & 1 & 0 \\1 & 0 & 0 \\1 & 0 & 0 \\0 & 0 & 1\end{bmatrix}$ $\frac{1}{2}\begin{bmatrix}0 & 1 & 0 \\1 & 0 & 0 \\{- 1} & 0 & 0 \\0 & 0 & 1\end{bmatrix}$ Index  8 to 11 $\frac{1}{2}\begin{bmatrix}0 & 1 & 0 \\1 & 0 & 0 \\0 & 0 & 1 \\1 & 0 & 0\end{bmatrix}$ $\frac{1}{2}\begin{bmatrix}0 & 1 & 0 \\1 & 0 & 0 \\0 & 0 & 1 \\{- 1} & 0 & 0\end{bmatrix}$ $\frac{1}{2}\begin{bmatrix}0 & 1 & 0 \\0 & 0 & 1 \\1 & 0 & 0 \\1 & 0 & 0\end{bmatrix}$ $\frac{1}{2}\begin{bmatrix}0 & 1 & 0 \\0 & 0 & 1 \\1 & 0 & 0 \\{- 1} & 0 & 0\end{bmatrix}$

[Table 7] illustrates precoding matrices included in a precodingcodebook available for transmission of 4 layers (i.e. rank-4transmission) in the uplink spatial multiplexing transmission schemeusing 4 Tx antennas. For 4-Tx rank-4 transmission, only one precodingmatrix may be used.

TABLE 7 Codebook Index 0 $\frac{1}{2}\begin{bmatrix}1 & 0 & 0 & 0 \\0 & 1 & 0 & 0 \\0 & 0 & 1 & 0 \\0 & 0 & 0 & 1\end{bmatrix}$

For reliable uplink multi-antenna transmission, the following operationsmay be considered. First of all, a UE may transmit an RS and an eNB mayacquire spatial channel information about an uplink directed from the UEto the eNB from the RS. The eNB may select a rank suitable for uplinktransmission, acquire a precoding weight, and calculate Channel QualityInformation (CQI) based on the acquired spatial channel information. TheeNB may signal control information for uplink signal transmission to theUE. The control information may include uplink transmission resourceassignment information, MIMO information (a rank, a precoding weight,etc.), an MCS level, HARQ information (an RV, an NDI, etc.), and uplinkDM-RS sequence information. The UE may transmit an uplink signal usingthe control information received from the eNB.

The present invention proposes a specific method for efficientlyconfiguring MCS information, HARQ information, and MIMO informationamong control information that an eNB signals to a UE for uplinkmulti-antenna transmission.

In an MCW multi-antenna system, codeword-to-layer mapping relationshipsmay be defined as illustrated in [Table] 1. As noted from [Table] 1,when a single CW is used, a transmission rank may be 1 or 2. Especially,rank-2 transmission of one CW may be limited to retransmission. When twoCWs are used, the transmission rank may be 2, 3 or 4.

When up to two CWs are used for transmission, control information mayinclude two MCS levels, two RVs, and two NDIs. This control informationfor MCW uplink transmission may be transmitted to a UE in a DCI formaton a PDCCH.

In the control information, for example, an MCS field may be 5 bits.[Table 8] and [Table 9] illustrate exemplary configurations of an MCSfield for downlink data transmission (a PDSCH) and uplink datatransmission (a PUSCH). As illustrated in [Table 8], an MCS field may beconfigured for a PDSCH to represent 29 states that indicate MCSs bycombining modulation orders and Transport Block Sizes (TBSs) and 3states indicating MCSs by modulation orders only. In addition, Asillustrated in [Table 9], an MCS field may be configured for a PUSCH torepresent 29 states indicated by combining modulation orders, TBSindexes, and RV value ‘0’ and 3 states indicated by RVs only.

TABLE 8 MCS Index Modulation Order TBS Index I_(MCS) Q_(m) I_(TBS) 0 2 01 2 1 2 2 2 3 2 3 4 2 4 5 2 5 6 2 6 7 2 7 8 2 8 9 2 9 10 4 9 11 4 10 124 11 13 4 12 14 4 13 15 4 14 16 4 15 17 6 15 18 6 16 19 6 17 20 6 18 216 19 22 6 20 23 6 21 24 6 22 25 6 23 26 6 24 27 6 25 28 6 26 29 2reserved 30 4 31 6

TABLE 9 MCS Modulation TBS Redundancy Index Order Index Version I_(MCS)Q_(m) ^(′) I_(TBS) rv_(idx) 0 2 0 0 1 2 1 0 2 2 2 0 3 2 3 0 4 2 4 0 5 25 0 6 2 6 0 7 2 7 0 8 2 8 0 9 2 9 0 10 2 10 0 11 4 10 0 12 4 11 0 13 412 0 14 4 13 0 15 4 14 0 16 4 15 0 17 4 16 0 18 4 17 0 19 4 18 0 20 4 190 21 6 19 0 22 6 20 0 23 6 21 0 24 6 22 0 25 6 23 0 26 6 24 0 27 6 25 028 6 26 0 29 reserved 1 30 2 31 3

[Table 8] is an MCS table for downlink data transmission. Controlinformation for downlink transmission may include MCS bits, an RV bit,and an NDI bit. A modulation order, a coding rate, and an RV may bedetermined for new transmission and retransmission by combining theseinformation.

In an MCS MIMO system that transmits a plurality of CWs, if a CW isdisabled (e.g. when a buffer of a transmitter transmits almost all dataas intended and a CW is unnecessary, or only one CW remains to beretransmitted during HARQ transmission), disabling of the CW may beindicated by the following signaling.

If I_(MCS)=0 and rv_(idx)=1 in DCI formats 2 and 2A for downlink PDSCHtransmission, this may mean that a TB is disabled. Otherwise, it maymean that a TB is enabled. That is, whether a CW is enabled or disabledmay be indicated by using an MCS field and an RV field in combination.

[Table 9] illustrates an MCS table for uplink single CW transmission.Control information for uplink transmission includes MCS bits and an NDIbit, and RV information is included in the MCS table (i.e. the RVinformation and MCS information are jointly encoded). Compared to thecontrol information for downlink data transmission, the controlinformation for uplink data transmission does not include an RV field.

In regards to configuring control information for uplink MCWtransmission, no method for indicating a disabled CW has been specified.It is difficult to apply a method for indicating a disabled CW on adownlink as defined in the legacy LTE system (e.g. 3GPP LTE release-8)(i.e. if I_(MCS)=0 and rv_(idx)=1, it indicates that a corresponding CWis disabled) to control information for uplink MCW transmission.Therefore, the present invention proposes methods for configuring newcontrol information that indicates a disabled CW in uplink MCW MIMOtransmission.

Methods for Configuring Control Information Indicating Disabled UplinkTB

Method 1

In Method 1, whether a CW is disabled in uplink MCW transmission isindicated by redefining one or more states defined in a conventional MCStable for other usages.

In Embodiment 1-1, it is assumed that MCS fields are defined to supporttwo CWs and a part of an MCS field for a second TB may be redefined forother usage.

In Embodiment 1-2, among 32 states represented by an MCS field, if someMCS states are represented by combining modulation orders, TBSs, and RVvalue ‘0’ (e.g. MCS index #0 to #28 in Table 9), an MCS state indicatingthe lowest modulation order and the smallest TBS may be redefined torepresent a TB disabled state. For example, MCS index #0 indicating thelowest modulation order and the smallest TBS may be redefined torepresent a TB disabled state.

In Embodiment 1-3, among 32 states represented by an MCS field, if someMCS states are represented by combining modulation orders, TBSs, and RVvalue ‘0’ (e.g. MCS index #0 to #28 in [Table 9]), an MCS stateindicating the highest modulation order and the largest TBS may beredefined to represent a TB disabled state. For example, MCS index #28indicating the highest modulation order and the largest TBS may beredefined to represent a TB disabled state.

In Embodiment 1-4, when two MCS fields are defined, a part of statesindicating only RVs (e.g. MCS index #29 and #30 in [Table 9]) may beredefined to represent a TB disabled state among states represented by asecond MCS field for a second TB. For example, MCS index #31 indicatesthat an MCS and a TBS are reserved and an RV is ‘3’ in [Table 9]. ThenMCS index #31 in the MCS field for the second TB may be used to indicatethe TB disabled state. However, MCS index #31 is purely exemplary andthus MCS indexes #29 and #30 may be used for the same usage.

In Embodiment 1-5, a part of MCS states indicating only RVs may beredefined to represent TB disabled among MCS states represented by anMCS table. Compared to Embodiment 1-4, the TB disabled state isredefined for each of a plurality of MCS tables. For example, MCS index#31 indicates that an RV is ‘3’ and an MCS and a TBS are reserved in[Table 9]. Then MCS index #31 for the MCS field for the second TB may beused to indicate TB disabled. However, MCS index #31 is purely exemplaryand thus MCS indexes #29 and #30 may be used for the same usage.

In Embodiment 1-6, a part of states indicating modulation orders andTBSs that have the same spectral efficiency may be used to indicate TBdisabled among fields defined in an MCS table.

Method 2

In Method 2, a new MCS table is defined with a part of a conventional5-bit MCS table. Accordingly, the new MCS table may have a smaller sizethan the conventional MCS table, for example, 2 or 3 bits.

States having equidistant TBS indexes in the conventional MCS table mayform a new MCS table. The new MCS table may include information about CWdisabling. That is, a specific state may be defined as the TB disabledstate in the new 2-bit or 3-bit MCS table.

Method 3

Method 3 interprets a conventional MCS field and NDI field in adifferent manner. That is, an MCS field including a modulation order, aTBS, and RV information and an NDI field are considered together. Thus,a specific combination may be interpreted to represent the TB disabledstate.

In the MCS field for PUSCH transmission, MCS indexes #29 to #31 are usedto indicate new RVs. Herein, MCS indexes #29 to #31 indicating new RVsare used only for retransmission and a modulation order forretransmission is the same as for initial transmission. An NDI bit isnot toggled at retransmission (e.g. If the NDI is 0 at initialtransmission, the NDI is still 0 at retransmission. If the NDI is 1 atinitial transmission, the NDI is still 1 at retransmission). That is, ifMCSs #29 to #31 are indicated for retransmission, the NDI bit isbasically not toggled. In other words, a combination of indication ofMCSs #29 to #31 and toggling of an NDI bit has not been defined in theconventional control information configuration. The present inventionproposes a method for indicting a TB disabled state by combining an MCSfield with an NDI bit.

In transmission of two or more TBs, a combination of an MCS indexindicating an RV only and an NDI bit value may be considered as a methodfor indicating a disabled TB.

Specifically, if an MCS field indicates only an RV (i.e. indicates oneof MCS indexes #29 to #31) and an NDI bit has been toggled from aprevious transmission, this may be newly interpreted as indicating TBdisabled.

When the NDI bit is toggled to indicate TB disabled, an HARQ buffer maybe flushed.

If a buffer for a disabled TB is flushed, the NDI bit is toggled at thenext transmission, and the MCS field indicates a modulation order, aTBS, and RV ‘0’ like MCS indexes #0 to #28, a new transmission isattempted.

Meanwhile, if an HARQ process in which a TB is disabled occurs duringACK/NACK signal transmission on two PHICHs, ACK/NACK information for oneTB may be represented using one PHICH resource. For instance, in case oflayer shifting, it can be said that the error probabilities of two CWs(or TBs) are equal. Therefore, one PHICH resource is sufficient torepresent ACK/NACK information.

In the case where ACK/NACK signals are transmitted on a PHICHrepresenting a plurality of states to support MCS, when a TB isdisabled, an ACK/NACK may be represented for a transmitted TB using aPHICH having a state indicating the number of transmitted TBs.

As described before, if reception success or failure of two TBs can beindicated by one HARQ ACK/NACK, a single NDI field may indicate that thetwo TBs are new data or retransmission data, instead of two NDI fields.Accordingly, one NDI field may be defined for each TB or all TBs.

The following bit fields may be configured as control information forsupporting MCW MIMO transmission by considering the above descriptioncomprehensively.

In Case 1, control information may be configured so as to have two MCSfields (of the same bit size) and two NDI fields.

For a first TB,

MCS: 5 bits

NDI: 1 bit.

For a second TB,

MCS: 5 bits

NDI: 1 bit.

If control information is configured as in Case 1, implementation ofEmbodiment 1-2 or 1-3 in Method 1 will be described. For example, if anMCS field for one TB indicates RV ‘0’, the lowest modulation order, andthe smallest TBS (i.e. MCS index #0) or if the MCS field indicates RV‘0’, the highest modulation order, and the largest TBS (i.e. MCS index#28), this may mean that the TB is disabled. In other words, ifI_(MCS)=0 or I_(MCS)=28 in an MCS table defined for a TB in a DCI formatfor uplink SU-MIMO transmission, the TB is disabled. Otherwise, it mayindicate that the TB is enabled.

In Case 2, control information may be configured so as to have two MCSfields (of the same bit size) and one NDI field.

For a first TB,

MCS: 5 bits

NDI: 1 bit.

For a second TB,

MCS: 5 bits

In Case 3, control information may be configured in such a manner thatone of two MCS fields has a bit size equal to a part of the bit size ofthe other MCS field (see Method 2) and two NDI fields are defined.

For a first TB,

MCS: 5 bits

NDI: 1 bit.

For a second TB,

MCS: N (N<5) bits

NDI: 1 bit.

In Case 4, control information may be configured in such a manner thatone of two MCS fields has a bit size equal to a part of the bit size ofthe other MCS field (see Method 2) and one NDI field is defined.

For a first TB,

MCS: 5 bits

NDI: 1 bit.

For a second TB,

MCS: N (N<5) bits

As described before, various MCS and NDI combinations may be producedfor uplink MCW MIMO transmission. In addition, an enabled or disabled CWcan be indicated by interpreting an MCS field in the above-describedmanners.

Methods for Indicating Uplink Precoding Information

As described before, whether a TB is enabled or disabled in uplink MIMOtransmission may be signaled by control information that schedulesuplink MIMO transmission (a DCI format). The present invention proposesa method for configuring control information that efficiently indicatesprecoding information for MIMO transmission, using the number of enabledTBs indicated through interpretation of the control information asinformation.

As described before in relation to a transport block-to-codeword mappingrelationship, when two TBs are enabled, one of the TBs may be mapped toa first CW CW0 and the other TB may be mapped to a second CW CW1(swapping of transport block-to-codeword mapping is included). If onlyone of the two TBs is enabled, the enabled TB is mapped to the first CW,CW0.

First of all, the size of necessary precoding information according toan uplink transmission rank (i.e. the number of antenna ports used foruplink transmission) will be described again. As described before withreference to [Table 3], when a UE has 2 Tx antennas, one of 6 precodingmatrices may be used for rank-1 transmission and one precoding matrixmay be used for rank-2 transmission. Therefore, for 2 Tx antennas, sizesof necessary precoding information may be summarized in [Table 10]below.

TABLE 10 Precoding information size Rank-1 6 Rank-2 1

As described before with reference to [Table 4] to [Table 7], when a UEhas 4 Tx antennas, one of 24 precoding matrices may be used for rank-1transmission, one of 16 precoding matrices may be used for rank-2transmission, one of 12 precoding matrices may be used for rank-3transmission, and one precoding matrix may be used for rank-4transmission. Hence, sizes of precoding information needed for 4 Txantennas may be summarized in [Table 11] below.

TABLE 11 Precoding information size Rank-1 24 Rank-2 16 Rank-3 12 Rank-41

Uplink transmission ranks that are available according to numbers ofenabled CWs may be summarized, taking into account a codeword-to-layermapping relationship in [Table 12] and [Table 13]. [Table 12] listsranks according to numbers of enabled CWs, for 2 Tx antennas and [Table13] lists ranks according to numbers of enabled CWs, for 4 Tx antennas.

TABLE 12 One CW Two CW Rank-1 Rank-2

TABLE 13 One CW Two CW Rank-1 Rank-2 Rank-2 Rank-3 Rank4

According to [Table 10] to [Table 13], the size of necessary precodinginformation (i.e. the number of states represented by a precodinginformation field) may be defined according to the number of enabledCWs. For example, [Table 14] and [Table 15] may be built by substitutingthe sizes of precoding information based on ranks listed in [Table 10]and [Table 11] into [Table 12] and [Table 13]. [Table 14] is for 2 Txantennas and [Table 14] is for 4 Tx antennas. As described before,whether only one CW or both CWs are enabled in [Table 14] and [Table 15]may be indicated by interpreting an MCS field and/or other informationin uplink MIMO control information (a DCI format) as proposed in Method1, Method 2 and Method 3.

TABLE 14 One CW enabled Two CWs enabled Rank-1 Rank-2 6-state precodinginformation 1-state precoding information

TABLE 15 One CW Two CW Rank-1 Rank-2 24-state precoding information16-state precoding information Rank-2 Rank-3 16-state precodinginformation 12-state precoding information Rank4 1-state precodinginformation

As illustrated in [Table 14], all precoding information for 2 Txantennas may be represented in 3 bits (a total of 8 states can berepresented). As illustrated in [Table 15], all precoding informationfor 4 Tx antennas may be represented in 6 bits (a total of 64 states canbe represented).

A precoding information field may be interpreted differently accordingto the number of enabled CWs. The number of enabled CWs may be knowndepending on whether a TB is enabled or not in Method 1, Method 2, andMethod 3. For example, when two TBs are enabled, it may be determinedthat two CWs are enabled. On the other hand, if one of the two TBs isdisabled, it may be determined that only the first CW, CW0 is enabled.Since the number of enabled CWs can be determined in this manner, theprecoding information field may indicate rank information and aprecoding matrix index differently according to the number of enabledCWs.

More specifically, for 2 Tx antennas for uplink transmission (in thecase of [Table 14]), when one CW is enabled, each of 6 states ofprecoding information indicates rank-1 transmission and a precodingmatrix to be used for uplink transmission. For example, if the bit valueof precoding information is 0, this indicates a precoding matrix withcodebook index 0 and if the bit value of precoding information is 1,this indicates a precoding matrix with codebook index 1 in the case of 1layer in [Table 3]. Meanwhile, in the case where the bit value of theprecoding information is 0, if two CWs are enabled, this indicatesrank-2 transmission and a precoding matrix with codebook index 0 in thecase of 2 layers in [Table 3]. In other words, even though the precodinginformation has the same bit value, the precoding information mayrepresent different rank information and precoding matrix informationaccording to the number of enabled CWs.

Similarly, for 3 Tx antennas for uplink transmission, precodinginformation having the same bit value may represent different rankinformation and precoding matrix information according to the number ofenabled CWs. For example, it is assumed that precoding information has abit value of 4 in [Table 15]. If one CW is enabled, the precodinginformation may represent rank-1 transmission and a precoding matrixwith codebook index 4 in [Table 5].

Since a precoding information field indicating every possible precodingmatrix for uplink SU-MIMO information can be configured in a minimumnumber of bits, the present invention can efficiently provide uplinkscheduling control information by reducing signaling overhead.

Meanwhile, if the size of a precoding information field is defined asdescribed before, remaining states that are represented by precodinginformation may be reserved for other control information.

A reserved bit of the precoding information field may be used torepresent a state where single antenna transmission or 1-CW transmissionis allowed, when MIMO transmission is set.

For instance, when MIMO transmission is set but control information forMIMO transmission is not sufficiently secured, a simplest transmissionscheme may be supported to be used until MIMO transmission isstabilized. For example, since single-antenna transmission enables datatransmission with minimum channel information, a reserved state ofprecoding information may be defined as a state that allowssingle-antenna transmission. Accordingly, precoding information may beconfigured as illustrated in [Table 16] and [Table 17].

TABLE 16 One CW enabled Two CWs enabled Rank-1 Rank-2 6-state precodinginformation 1-state precoding information Single antenna transmission(or any transmission scheme using one CW)

TABLE 17 One CW Two CWs Rank-1 Rank-2 24-state precoding information16-state precoding information Rank-2 Rank-3 16-state precodinginformation 12-state precoding information Single antenna transmissionRank-4 (or any transmission scheme 1-state precoding information usingone CW)

Bits indicating precoding information may be efficiently used byreducing the number of states represented by the precoding information.For example, the bits of precoding information may be decreased from 6bits to 5 bits.

For this purpose, a precoding weight for rank-2 transmission of one CWmay be expressed as a subset of a precoding weight for rank-2transmission of two CWs. For example, when a rank-2 precoding weightincludes 16 elements, a part of the elements may be used as a precodingweight for rank-2 transmission of one CW.

For example, when only one CW is enabled, precoding information may beconfigured only with a rank-1 codebook and a rank-2 codebook. The rank-2codebook represents N (N≦12) states. [Table 18] to [Table 21] illustratecases where a rank-2 codebook for transmission of one CW has 12, 8, 6and 4 states, respectively, for 4 Tx antennas.

TABLE 18 One CW Two CW Rank-1 Rank-2 24-state precoding information16-state precoding information Rank-2 Rank-3 12-state precodinginformation 12-state precoding information Rank4 1-state precodinginformation Reserved (3-states)

TABLE 19 One CW Two CW Rank-1 Rank-2 24-state precoding information16-state precoding information Rank-2 Rank-3 8-state precodinginformation 12-state precoding information Rank4 1-state precodinginformation Reserved (3-states)

TABLE 20 One CW Two CW Rank-1 Rank-2 24-state precoding information16-state precoding information Rank-2 Rank-3 6-state precodinginformation 12-state precoding information Reserved (2-states) Rank41-state precoding information Reserved (3-states)

TABLE 21 One CW Two CW Rank-1 Rank-2 24-state precoding information16-state precoding information Rank-2 Rank-3 4-state precodinginformation 12-state precoding information Reserved (4-states) Rank41-state precoding information Reserved (3-states)

In another example, when only one CW is enabled, precoding informationis configured so as to represent states for a rank-1 codebook, a rank-2codebook, and the simplest transmission scheme (e.g. single-antennatransmission). The rank-2 codebook represents N (N≦11) states. [Table22] to [Table 25] illustrate cases where the rank-2 codebook represents11, 8, 6 and 4 states, respectively in case of one CW transmission, for4 Tx antennas.

TABLE 22 One CW Two CWs Rank-1 Rank-2 24-state precoding information16-state precoding information Rank-2 Rank-3 11-state precodinginformation 12-state precoding information Single antenna transmissionRank-4 (or any transmission scheme 1-state precoding information usingone CW) Reserved (3-states)

TABLE 23 One CW Two CWs Rank-1 Rank-2 24-state precoding information16-state precoding information Rank-2 Rank-3 8-state precodinginformation 12-state precoding information Single antenna transmissionRank-4 (or any transmission scheme 1-state precoding information usingone CW) Reserved (3-states)

TABLE 24 One CW Two CWs Rank-1 Rank-2 24-state precoding information16-state precoding information Rank-2 Rank-3 6-state precodinginformation 12-state precoding information Single antenna transmissionRank-4 (or any transmission scheme 1-state precoding information usingone CW) Reserved (1-state) Reserved (3-states)

TABLE 25 One CW Two CWs Rank-1 Rank-2 24-state precoding information16-state precoding information Rank-2 Rank-3 4-state precodinginformation 12-state precoding information Single antenna transmissionRank-4 (or any transmission scheme 1-state precoding information usingone CW) Reserved (3-states) Reserved (3-states)

In the above methods for configuring precoding information, examples ofconfiguring a rank-2 code book for 1-CW transmission using a subset of arank-2 codebook for 2-CW transmission are illustrated in [Table 26] to[Table 31]. [Table 26] to [Table 31] illustrate cases where a rank-2codebook for 1-CW transmission represents 3, 4, 6, 8, 11 and 12 states,respectively by combining some (N) of 16 states represented by a rank-2codebook for 2-CW transmission.

TABLE 26 N = 3: 16C3 combinations ${\frac{1}{2}\begin{bmatrix}1 & 0 \\1 & 0 \\0 & 1 \\0 & {- j}\end{bmatrix}},{\frac{1}{2}\begin{bmatrix}1 & 0 \\0 & 1 \\1 & 0 \\0 & 1\end{bmatrix}},{\frac{1}{2}\begin{bmatrix}1 & 0 \\0 & 1 \\0 & 1 \\1 & 0\end{bmatrix}}$

TABLE 27 N = 4: 16C4 combinations ${\frac{1}{2}\begin{bmatrix}1 & 0 \\1 & 0 \\0 & 1 \\0 & {- j}\end{bmatrix}},{\frac{1}{2}\begin{bmatrix}1 & 0 \\1 & 0 \\0 & 1 \\0 & j\end{bmatrix}},{\frac{1}{2}\begin{bmatrix}1 & 0 \\{- j} & 0 \\0 & 1 \\0 & 1\end{bmatrix}},{\frac{1}{2}\begin{bmatrix}1 & 0 \\{- j} & 0 \\0 & 1 \\0 & {- 1}\end{bmatrix}}$

TABLE 28 N = 6: 16C6 combinations $\frac{1}{2}\begin{bmatrix}1 & 0 \\1 & 0 \\0 & 1 \\0 & {- j}\end{bmatrix}$ $\frac{1}{2}\begin{bmatrix}1 & 0 \\1 & 0 \\0 & 1 \\0 & j\end{bmatrix}$ $\frac{1}{2}\begin{bmatrix}1 & 0 \\{- j} & 0 \\0 & 1 \\0 & 1\end{bmatrix}$ $\frac{1}{2}\begin{bmatrix}1 & 0 \\{- j} & 0 \\0 & 1 \\0 & {- 1}\end{bmatrix}$ $\frac{1}{2}\begin{bmatrix}1 & 0 \\{- 1} & 0 \\0 & 1 \\0 & {- j}\end{bmatrix}$ $\frac{1}{2}\begin{bmatrix}1 & 0 \\{- 1} & 0 \\0 & 1 \\0 & j\end{bmatrix}$

TABLE 29 N = 8: 16C8 combinations Index 0 to 3$\frac{1}{2}\begin{bmatrix}1 & 0 \\1 & 0 \\0 & 1 \\0 & {- j}\end{bmatrix}$ $\frac{1}{2}\begin{bmatrix}1 & 0 \\1 & 0 \\0 & 1 \\0 & j\end{bmatrix}$ $\frac{1}{2}\begin{bmatrix}1 & 0 \\{- j} & 0 \\0 & 1 \\0 & 1\end{bmatrix}$ $\frac{1}{2}\begin{bmatrix}1 & 0 \\{- j} & 0 \\0 & 1 \\0 & {- 1}\end{bmatrix}$ Index 4 to 7 $\frac{1}{2}\begin{bmatrix}1 & 0 \\{- 1} & 0 \\0 & 1 \\0 & {- j}\end{bmatrix}$ $\frac{1}{2}\begin{bmatrix}1 & 0 \\{- 1} & 0 \\0 & 1 \\0 & j\end{bmatrix}$ $\frac{1}{2}\begin{bmatrix}1 & 0 \\j & 0 \\0 & 1 \\0 & 1\end{bmatrix}$ $\frac{1}{2}\begin{bmatrix}1 & 0 \\j & 0 \\0 & 1 \\0 & {- 1}\end{bmatrix}$

TABLE 30 N = 11: 16C11 = 16C5 Index 0 to 3 $\frac{1}{2}\begin{bmatrix}1 & 0 \\1 & 0 \\0 & 1 \\0 & {- j}\end{bmatrix}$ $\frac{1}{2}\begin{bmatrix}1 & 0 \\1 & 0 \\0 & 1 \\0 & j\end{bmatrix}$ $\frac{1}{2}\begin{bmatrix}1 & 0 \\{- j} & 0 \\0 & 1 \\0 & 1\end{bmatrix}$ $\frac{1}{2}\begin{bmatrix}1 & 0 \\{- j} & 0 \\0 & 1 \\0 & {- 1}\end{bmatrix}$ Index 4 to 7 $\frac{1}{2}\begin{bmatrix}1 & 0 \\{- 1} & 0 \\0 & 1 \\0 & {- j}\end{bmatrix}$ $\frac{1}{2}\begin{bmatrix}1 & 0 \\{- 1} & 0 \\0 & 1 \\0 & j\end{bmatrix}$ $\frac{1}{2}\begin{bmatrix}1 & 0 \\j & 0 \\0 & 1 \\0 & 1\end{bmatrix}$ $\frac{1}{2}\begin{bmatrix}1 & 0 \\j & 0 \\0 & 1 \\0 & {- 1}\end{bmatrix}$ Index  8 to 10 $\frac{1}{2}\begin{bmatrix}1 & 0 \\0 & 1 \\1 & 0 \\0 & 1\end{bmatrix}$ $\frac{1}{2}\begin{bmatrix}1 & 0 \\0 & 1 \\1 & 0 \\0 & {- 1}\end{bmatrix}$ $\frac{1}{2}\begin{bmatrix}1 & 0 \\0 & 1 \\{- 1} & 0 \\0 & 1\end{bmatrix}$

TABLE 31 N = 12: 16C12 = 16C4 Index 0 to 3 $\frac{1}{2}\begin{bmatrix}1 & 0 \\1 & 0 \\0 & 1 \\0 & {- j}\end{bmatrix}$ $\frac{1}{2}\begin{bmatrix}1 & 0 \\1 & 0 \\0 & 1 \\0 & j\end{bmatrix}$ Index 4 to 7 $\frac{1}{2}\begin{bmatrix}1 & 0 \\{- 1} & 0 \\0 & 1 \\0 & {- j}\end{bmatrix}$ $\frac{1}{2}\begin{bmatrix}1 & 0 \\{- 1} & 0 \\0 & 1 \\0 & j\end{bmatrix}$ Index  8 to 11 $\frac{1}{2}\begin{bmatrix}1 & 0 \\0 & 1 \\1 & 0 \\0 & 1\end{bmatrix}$ $\frac{1}{2}\begin{bmatrix}1 & 0 \\0 & 1 \\1 & 0 \\0 & {- 1}\end{bmatrix}$ $\frac{1}{2}\begin{bmatrix}1 & 0 \\0 & 1 \\{- 1} & 0 \\0 & 1\end{bmatrix}$ $\frac{1}{2}\begin{bmatrix}1 & 0 \\0 & 1 \\{- 1} & 0 \\0 & {- 1}\end{bmatrix}$ Index 12 to 15 $\frac{1}{2}\begin{bmatrix}1 & 0 \\0 & 1 \\0 & 1 \\1 & 0\end{bmatrix}$ $\frac{1}{2}\begin{bmatrix}1 & 0 \\0 & 1 \\0 & {- 1} \\1 & 0\end{bmatrix}$ $\frac{1}{2}\begin{bmatrix}1 & 0 \\0 & 1 \\0 & 1 \\{- 1} & 0\end{bmatrix}$ $\frac{1}{2}\begin{bmatrix}1 & 0 \\0 & 1 \\0 & {- 1} \\{- 1} & 0\end{bmatrix}$

The precoding information field may be configured as illustrated in[Table 32], [Table 33], and [Table 34], taking the above descriptioninto comprehensive account. [Table 32] illustrates contents of a 3-bitprecoding information field for 2 Tx antennas, [Table 33] illustratescontents of a 5-bit precoding information field for 4 Tx antennas, and[Table 34] illustrates contents of a 6-bit precoding information fieldfor 4 Tx antennas.

TABLE 32 One codeword: Two codeword: Codeword 0 enabled Codeword 0enabled Codeword 1 disabled Codeword 1 enabled Bit field Bit fieldmapped mapped to index Message to index Message 0 1 layer: singleantenna 0 2 layers: Precoding corresponding to precoding matrix  $\frac{1}{\sqrt{2}}\begin{bmatrix}1 & 0 \\0 & 1\end{bmatrix}$ 1 1 layer: Precoding 1-7 reserved corresponding toprecoding matrix [1 1]^(T)/{square root over (2)} 2 1 layer: Precodingcorresponding to precoding matrix [1 −1]^(T)/{square root over (2)} 3 1layer: Precoding corresponding to precoding matrix [1 j]^(T)/{squareroot over (2)} 4 1 layer: Precoding corresponding to precoding matrix [1−j]^(T)/{square root over (2)} 5 1 layer: Precoding corresponding toprecoding matrix [1 0]^(T)/{square root over (2)} 6 1 layer: Precodingcorresponding to precoding matrix [0 1]^(T)/{square root over (2)} 7reserved

TABLE 33 One codeword: Two codeword: Codeword 0 enabled Codeword 0enabled Codeword 1 disabled Codeword 1 enabled Bit field Bit fieldmapped mapped to index Message to index Message 0 1 layer: singleantenna 0 2 layers: TPMI 0 1 1 layer: TPMI 0 1 2 layers: TPMI 1 2 1layer: TPMI 1 2 2 layers: TPMI 2 3 1 layer: TPMI 2 3 2 layers: TPMI 3 41 layer: TPMI 3 4 2 layers: TPMI 4 5 1 layer: TPMI 4 5 2 layers: TPMI 56 1 layer: TPMI 5 6 2 layers: TPMI 6 7 1 layer: TPMI 6 7 2 layers: TPMI7 8 1 layer: TPMI 7 8 2 layers: TPMI 8 9 1 layer: TPMI 8 9 2 layers:TPMI 9 10 1 layer: TPMI 9 10 2 layers: TPMI 10 11 1 layer: TPMI 10 11 2layers: TPMI 11 12 1 layer: TPMI 11 12 2 layers: TPMI 12 13 1 layer:TPMI 12 13 2 layers: TPMI 13 14 1 layer: TPMI 13 14 2 layers: TPMI 14 151 layer: TPMI 14 15 2 layers: TPMI 15 16 1 layer: TPMI 15 16 3 layers:TPMI 0 17 1 layer: TPMI 16 17 3 layers: TPMI 1 18 1 layer: TPMI 17 18 3layers: TPMI 2 19 1 layer: TPMI 18 19 3 layers: TPMI 3 20 1 layer: TPMI19 20 3 layers: TPMI 4 21 1 layer: TPMI 20 21 3 layers: TPMI 5 22 1layer: TPMI 21 22 3 layers: TPMI 6 23 1 layer: TPMI 22 23 3 layers: TPMI7 24 1 layer: TPMI 23 24 3 layers: TPMI 8 25 2 layers: TPMI a 25 3layers: TPMI 9 26 2 layers: TPMI b 26 3 layers: TPMI 10 27 2 layers:TPMI c 27 3 layers: TPMI 11 28 2 layers: TPMI d 28 4 layers: Precodingcorresponding to precoding matrix   $\frac{1}{2}\begin{bmatrix}1 & 0 & 0 & 0 \\0 & 1 & 0 & 0 \\0 & 0 & 1 & 0 \\0 & 0 & 0 & 1\end{bmatrix}$ 29 2 layers: TPMI e 29-31 Reserved 30 2 layers: TPMI f 31Reserved

TABLE 34 One codeword: Two codeword: Codeword 0 enabled Codeword 0enabled Codeword 1 disabled Codeword 1 enabled Bit field Bit fieldmapped mapped to index Message to index Message 0 1 layer: singleantenna 0 2 layers: TPMI 0 1 1 layer: TPMI 0 1 2 layers: TPMI 1 2 1layer: TPMI 1 2 2 layers: TPMI 2 3 1 layer: TPMI 2 3 2 layers: TPMI 3 41 layer: TPMI 3 4 2 layers: TPMI 4 5 1 layer: TPMI 4 5 2 layers: TPMI 56 1 layer: TPMI 5 6 2 layers: TPMI 6 7 1 layer: TPMI 6 7 2 layers: TPMI7 8 1 layer: TPMI 7 8 2 layers: TPMI 8 9 1 layer: TPMI 8 9 2 layers:TPMI 9 10 1 layer: TPMI 9 10 2 layers: TPMI 10 11 1 layer: TPMI 10 11 2layers: TPMI 11 12 1 layer: TPMI 11 12 2 layers: TPMI 12 13 1 layer:TPMI 12 13 2 layers: TPMI 13 14 1 layer: TPMI 13 14 2 layers: TPMI 14 151 layer: TPMI 14 15 2 layers: TPMI 15 16 1 layer: TPMI 15 16 3 layers:TPMI 0 17 1 layer: TPMI 16 17 3 layers: TPMI 1 18 1 layer: TPMI 17 18 3layers: TPMI 2 19 1 layer: TPMI 18 19 3 layers: TPMI 3 20 1 layer: TPMI19 20 3 layers: TPMI 4 21 1 layer: TPMI 20 21 3 layers: TPMI 5 22 1layer: TPMI 21 22 3 layers: TPMI 6 23 1 layer: TPMI 22 23 3 layers: TPMI7 24 1 layer: TPMI 23 24 3 layers: TPMI 8 25 2 layers: TPMI 1 25 3layers: TPMI 9 26 2 layers: TPMI 2 26 3 layers: TPMI 10 27 2 layers:TPMI 3 27 3 layers: TPMI 11 28 2 layers: TPMI 4 28 4 layers: Precodingcorresponding to precoding matrix   $\frac{1}{2}\begin{bmatrix}1 & 0 & 0 & 0 \\0 & 1 & 0 & 0 \\0 & 0 & 1 & 0 \\0 & 0 & 0 & 1\end{bmatrix}$ 29 2 layers: TPMI 5 29-63 Reserved 30 2 layers: TPMI 6 312 layers: TPMI 7 32 2 layers: TPMI 8 33 2 layers: TPMI 9 34 2 layers:TPMI 10 35 2 layers: TPMI 11 36 2 layers: TPMI 12 37 2 layers: TPMI 1338 2 layers: TPMI 14 39 2 layers: TPMI 15 40-63 Reserved

Control information (a DCI format) for uplink MCW MIMO transmission inthe 3GPP LTE-A system may be configured as follows, based on the abovedescription.

The legacy 3GPP LTE standard (e.g. 3GPP LTE Release-8) defines asingle-antenna port transmission mode for uplink transmission anddefines DCI format 0 to support the single-antenna port transmissionmode. DCI format 0 may include ‘Flag for format 0/format 1Adifferentiation’, ‘Hopping flag’, ‘Resource block allocation (forcontiguous allocation) and hopping resource allocation’, ‘MCS andredundancy version’, ‘NDI’, ‘TPC command for scheduled PUSCH’, ‘Cyclicshift for DMRS’, and ‘CQI request’.

Contiguous resource allocation and single-antenna transmission may besupported using DCI format 0. Meanwhile, non-contiguous resourceallocation and uplink spatial multiplexing transmission using up to 4transmission layers may be introduced to LTE-A uplink transmission. Tosupport this new uplink transmission scheme, it is necessary to define anew transmission mode and a new DCI format for control signaling of thenew transmission mode.

Considering uplink SU-MIMO spatial multiplexing, a closed-loop spatialmultiplexing transmission mode using multiple TBs and a closed-loopspatial multiplexing transmission mode using a single TB may be newlydefined as uplink transmission modes. In addition, the uplinksingle-antenna transmission mode as defined by 3GPP LTE Release-8 needsto be supported as a default transmission mode.

In the multi-TB closed-loop spatial multiplexing transmission mode,transmission of up to two TBs from a scheduled UE may be considered.Each individual TB may have an MCS level. To support dynamic rankadaptation, two MCS indicators for the two TBs may be included in uplinkscheduling control information (a DCI format). In addition, precodinginformation for all transmission ranks may be included in the controlinformation.

In the single-TB closed-loop spatial multiplexing transmission mode,support of rank-1 beamforming having low control signal overhead may beconsidered, similarly to downlink MIMO transmission of 3GPP LTERelease-8. For this transmission mode, uplink scheduling controlinformation (a DCI format) may include one MCS level and rank-1precoding information.

The single-antenna uplink transmission mode, which is a defaulttransmission mode, may be defined as an uplink transmission modeavailable before an eNB knows the Tx antenna configuration of a UE. Thistransmission mode may be used as a fall-back transmission mode of the3GPP LTE Release-10 uplink transmission mode.

To support the above LTE-A uplink SU-MIMO transmission modes, new uplinkscheduling control information (a new DCI format) needs to be defined.Requirements of control signaling to support uplink SU-MIMO transmissionwill be described below with reference to [Table 35].

TABLE 35 Number of bit Contents Mode A Mode B Comment Flag for UL/DLformat 0/1 0/1 differentiation Hopping flag 0/1 0/1 Resource block N + αN + α * N-bit for Rel-8 UL assignment allocation method * To support newmethod of resource allocation, α-bit can be added 1^(st) CW MCS and RV 55 NDI 1 1 2^(nd) CW MCS and RV 4-5 — NDI 1 — TB to codeword swap flag 1— Precoding information M Less 2Tx: 3-bit, 4Tx: 6-bit than M TPC commandfor 2 + β 2 + β * To support per antenna scheduled PUSCH power control,β-bit can be added. Cyclic shift for DMRS 3 3 OCC 0/1 0/1 UL index (forTDD) 2 2 Downlink Assignment 2 2 Index (for TDD) CQI request 1 1

[Table 35] illustrates an example of a new DCI format for PUSCHtransmission in the LTE-A system. In [Table 35], mode A is the multi-TBclosed-loop spatial multiplexing mode and mode B is the single-TBclosed-loop spatial multiplexing mode. Now a detailed description willbe given of each field in the DCI format of [Table 35].

The ‘Flag for UL/DL format differentiation’ field provides controlinformation indicating whether the DCI format is for UL transmission orDL transmission. Since the DCI format for uplink SU-MIMO transmissionhas the same size as the DCI format for downlink SU-MIMO transmission,the number of PDCCH blind decodings can be reduced. The number of bitsof the ‘Flag for UL/DL format differentiation’ field is 0 or 1. If thisfield is included in the DCI format, the field has 1 bit. When needed,this field is not included in the DCI format.

When non-contiguous resource allocation is used in the LTE-A system, the‘Hopping flag and resource block assignment’ field may not be neededbecause a frequency hopping mode may operate according to non-contiguousresource allocation. If a resource block assignment field fornon-contiguous assignment has the same size as a resource blockassignment field for LTE Release-8 uplink transmission, a new DCI formathaving the same size as the existing DCI format 0 may be designed.Non-contiguous resource assignment may be used for uplink SU-MIMOtransmission. The number of bits of the ‘Hopping flag and resource blockassignment’ field is 0 or 1. If this field is included in the DCIformat, the field has 1 bit. When needed, this field is not included inthe DCI format.

When layer shifting is not used for uplink SU-MIMO transmission, achannel carrying each CW is independent. For example, channelenvironments in which CWs are transmitted may be very different due toimbalance between transmission antennas and antenna gains. Therefore,independent ‘MCS and RV’ and ‘NDI’ fields may be defined for each CW foruplink SU-MIMO transmission, like control information for downlink MIMOtransmission in the LTE Release-8 system. The ‘MCS and RV’ and ‘NDI’fields for the first CW may be 5 bits and 1 bit long, respectively, asin the conventional DCI format 0. Like those of the first CW, the ‘MCSand RV’ and ‘NDI’ fields for the second CW may be 5 bits and 1 bit long,respectively. Or the ‘MCS and RV’ field for the second CW may have fewerthan 5 bits, as described before.

Meanwhile, if HARQ transmission is performed in a non-blanking fashion,new data may be transmitted for a CW for which an ACK has been receivedand retransmission data may be transmitted for a CW for which a NACK hasbeen received. On the other hand, if HARQ transmission is performed in ablanking fashion, new data may be transmitted if ACKs have been receivedfor two CWs. If an ACK has been received for one of the CWs and a NACKhas been received for the other CW, retransmission may be attempted forthe CW for which the NACK has been received, while no transmission maybe performed for the CW for which the ACK has been received. If NACKshave been received for the two CWs, retransmission may be performed forthe two CWs. To support non-blanking HARQ retransmission, an NDI fieldfor the second CW is needed in the DCI format.

Meanwhile, if one CW is mapped to one or two layers, it is necessary toindicate whether a TB is enabled or disabled in order to supporttransmission of one of two TBs. As described before, to indicate thestate of a disabled TB in uplink SU-MIMO transmission, some state of anMCS table may be interpreted differently or a state indicating TBdisabled may be added to the MCS table. For example, it may indicatethat a corresponding TB is disabled by signaling MCS index #0 or #28.

According to the ‘Precoding Information’ field, a 3-bit precodingcodebook may be used for a UE with 2 Tx antennas for uplink spatialmultiplexing, and a 6-bit precoding codebook may be used for a UE with 4Tx antennas for uplink spatial multiplexing. The precoding informationfield may be configured according to various embodiments of the presentinvention. For example, precoding information may be efficientlyconfigured as illustrated in [Table 12] to [Table 15], as describedbefore.

The ‘TB to Codeword swap flag’ field provides control informationindicating whether swapping occurs to TB to codeword mapping. When aspecific CW is transmitted through a specific physical antenna bymapping based on a codebook structure for LTE-A uplink MIMOtransmission, spatial diversity can be increased on a subframe basisthrough swapping.

The ‘Cyclic shift for DMRS’ field indicates a cyclic shift value appliedto an uplink DMRS. Uplink DMRSs may be multiplexed by separating theuplink DMRSs using cyclic shifts during multi-layer channel estimation.When cyclic shift indexes are assigned to multiple layers, the minimumnumber of bits required to indicate a cyclic shift is 3 bits. If acyclic shift is indicated for one layer, cyclic shift indexes may beallocated to other layers according to a predefined rule.

The ‘OCC’ field indicates an orthogonal cover code applied to uplinkDMRSs. The use of an OCC may increase orthogonal resources for uplinkDMRSs.

‘TPC command for scheduled PUSCH’ includes a transmission power commandfor transmission of a scheduled PUSCH. If a UE has multiple antennas,TPC commands may be applied to the respective antennas.

The ‘UL index (for TDD)’ field may indicate a subframe index set foruplink transmission in a specific uplink-downlink configuration, when aradio frame is configured in TDD mode.

The ‘Downlink Assignment Index (for TDD)’ field may specify the totalnumber of subframes set for PDSCH transmission in a specificuplink-downlink configuration, when a radio frame is configured in theTDD mode.

The ‘CQI request’ field indicates a request for reporting CQI, a PMI,and an RI non-periodically on a PUSCH. If the ‘CQI request’ field is setto 1, a UE transmits a non-periodical CQI, PMI, and RI report on aPUSCH.

Control information that schedules uplink SU-MIMO transmission can beefficiently provided, while reducing signaling overhead, by means of thenew DCI format.

FIG. 16 illustrates a method for providing control information thatschedules uplink multi-antenna transmission according to an embodimentof the present invention.

First, an operation of an eNB will be described. The eNB may generateDCI including MCS information for each of first and second TBs, TB1 andTb2 (S1610). The DCI is control information that schedules uplinktransmission of at least one of the TBs, TB1 and TB2. The eNB maytransmit the generated DCI to a UE on a PDCCH (S1620). The eNB mayreceive an uplink signal scheduled according to the DCI on a PUSCH fromthe UE (S1630).

Meanwhile, the UE may receive the DCI transmitted in step S1620 (S1640)and transmit at least one of the TBS, TB1 and TB2 on the PUSCH to theeNB according to the scheduling information included in the DCI (S1650).

If the MCS information for TB1 or TB2 has a specific value (e.g. MCSindex #0 or #28), it may indicate that the corresponding TB is disabled.

FIG. 17 illustrates a method for providing control information thatschedules uplink multi-antenna transmission according to anotherembodiment of the present invention.

An operation of an eNB will first be described below. The eNB maygenerate DCI including precoding information that specifies atransmission rank and a precoding matrix for uplink transmission(S1710). The DCI is control information that schedules uplinktransmission. The eNB may transmit the generated DCI to a UE on a PDCCH(S1720). The eNB may receive an uplink signal scheduled according to theDCI on a PUSCH from the UE (S1730).

Meanwhile, the UE may receive the DCI transmitted in S1720 (S1740) andtransmit uplink data on the PUSCH to the eNB according to thetransmission rank and the precoding matrix indicated by the schedulinginformation included in the DCI (S1750).

The size of precoding information included in the DCI may be determinedbased on the number of multiple antennas and the number of precodingmatrices available according to an uplink transmission rank. Inaddition, the precoding information may be configured so as to indicatea different transmission rank and precoding matrix according to thenumber of enabled CWs.

For 2 Tx antennas, when one CW is enabled, rank-1 transmission ispossible and when two CWs are enabled, rank-2 transmission is possible.For 4 Tx antennas, when one CW is enabled, rank-1 transmission or rank-2transmission is possible and when two CWs are enabled, rank-2transmission, rank-3 transmission, or rank-4 transmission is possible.

The number of enabled CWs is equal to that of enabled TBs. Disabling ofa TB may be indicated by a specific value (e.g. MCS index #0 or #28) setin an MCS field for each TB included in DCI as in Method 1, Method 2,and Method 3. Therefore, precoding information may be interpreteddifferently according to the number of enabled CWs. The size ofprecoding information may be determined based on a larger number ofstates according to the number of enabled CWs.

For 2 uplink Tx antennas, when one CW is enabled, precoding informationshould be able to represent 6 states indicating 6 precoding matrices forrank 1. When two CWs are enabled, the precoding information should beable to represent one state indicating one precoding matrix for rank 2.Therefore, the size of precoding information may be 3 bits (8 states).As described before, remaining states other than states indicatingtransmission ranks and precoding matrices may be reserved or used torepresent other information.

For 4 uplink Tx antennas, when one CW is enabled, precoding informationshould be able to represent 24 states indicating 24 precoding matricesfor rank 1 and 16 states indicating 16 precoding matrices for rank 2 (atotal of 40 states). When two CWs are enabled, the precoding informationshould be able to represent 16 states indicating 16 precoding matricesfor rank 2, 12 states indicating 12 precoding matrices for rank 3, andone state indicating one precoding matrix for rank 4 (a total of 29states). Therefore, the size of precoding information may be 6 bits (64states). As described before, remaining states other than statesindicating transmission ranks and precoding matrices may be reserved orused to represent other information.

A new DCI format may be configured by using the method for indicating adisabled TB (FIG. 16) and the method for configuring precodinginformation (FIG. 17) in combination, for uplink SU-MIMO transmission.In addition, DCI may be configured to schedule uplink multi-antennatransmission by applying one or more of the foregoing variousembodiments of the present invention simultaneously.

FIG. 18 is a block diagram of an eNB and a UE according to an embodimentof the present invention.

An eNB 1810 may include an Rx module 1811, a Tx module 1812, a processor1813, a memory 1814, and antennas 1815. The Rx module 1811 may receivedata and control signals from the outside (e.g. a UE). The Tx module1812 may transmit data and control signals to the outside (e.g. a UE).The processor 1813 may be connected to various components of the eNB1810 such as the Rx module 1811, the Tx module 1812, and the memory 1814in terms of communication and may provide overall control to the eNB1810 and its components. The eNB 1810 may support MIMO transmission andreception by a plurality of antennas 1815.

In accordance with an embodiment of the present invention, the eNB 1810may provide control information that schedules uplink multi-antennatransmission to the UE. The processor 1813 of the eNB 1810 may beconfigured so as to generate DCI including MCS information for each offirst and second TBs. The processor 1813 may generate DCI includingprecoding information that specifies a transmission rank and a precodingmatrix for uplink transmission. The processor 1813 may also transmit theDCI that schedules uplink transmission on a downlink control channelthrough the Tx module 1812. The processor 1813 may receive an uplinksignal scheduled based on the DCI on an uplink data channel through theRx module 1811.

If MCS information for one of the first and second TBs has apredetermined value (e.g. MCS index #0 or #28), it may indicate thecorresponding TB is disabled. The size of the precoding information maybe determined according to the number of multiple antennas and thenumber of precoding matrices available according to an uplinktransmission rank.

Besides, the processor 1813 may process information received at the eNB1810 and information to be transmitted to the outside. The memory 1814may store processed information for a predetermined time and may bereplaced by a component such as a buffer (not shown).

While the eNB 1810 has been described as an uplink receiver in FIG. 18,the same thing may apply to a Relay Node (RN) that is also an uplinkreceiver.

Meanwhile, a UE 1820 may include an Rx module 1821, a Tx module 1822, aprocessor 1823, a memory 1824, and antennas 1825. The Rx module 1821 mayreceive data and control signals from the outside (e.g. an eNB). The Txmodule 1822 may transmit data and control signals to the outside (e.g.an eNB). A processor 1823 may be connected to various components of theUE 1820 such as the Rx module 1821, the Tx module 1822, and the memory1824 in terms of communication and may provide overall control to the UE1820 and its component. The UE 1820 may support MIMO transmission andreception by a plurality of antennas 1825.

In accordance with an embodiment of the present invention, the UE 1820may perform uplink multi-antenna transmission. The processor 1823 of theUE 1820 may be configured so as to receive DCI that schedules uplinktransmission on a downlink control channel through the Rx module 1821.The processor 1823 may transmit an uplink signal scheduled according tothe received DCI on an uplink data channel through the Tx module 1822.

The DCI includes MCS information for each of first and second TBs. WhenMCS information for one of the first and second TBs has a predeterminedvalue (e.g. MCS index #0 or #28), it may indicate that the correspondingTB is disabled. In addition, the DCI may include precoding informationthat specifies a transmission rank and a precoding matrix for uplinktransmission. The size of the precoding information may be determinedaccording to the number of multiple antennas and the number of precodingmatrices available according to an uplink transmission rank.

Besides, the processor 1823 may process information received at the UE1820 and information to be transmitted to the outside. The memory 1824may store processed information for a predetermined time and may bereplaced by a component such as a buffer (not shown).

While the UE 1820 has been described as an uplink transmitter in FIG.18, the same thing may apply to an RN that is also an uplinktransmitter.

While components of the eNB and the UE according to the foregoingvarious embodiments of the present invention are not shown for clarityof description in relation to the BS and the UE illustrated in FIG. 18,it is clearly to be understood that the various embodiment of thepresent invention can be implemented in the eNB and the UE.

The embodiments of the present invention may be achieved by variousmeans, for example, hardware, firmware, software, or a combinationthereof.

In a hardware configuration, the methods according to the embodiments ofthe present invention may be achieved by one or more ApplicationSpecific Integrated Circuits (ASICs), Digital Signal Processors (DSPs),Digital Signal Processing Devices (DSDPs), Programmable Logic Devices(PLDs), Field Programmable Gate Arrays (FPGAs), processors, controllers,microcontrollers, microprocessors, etc.

In a firmware or software configuration, an embodiment of the presentinvention may be implemented in the form of a module, a procedure, afunction, etc. Software code may be stored in a memory unit and executedby a processor. The memory unit is located at the interior or exteriorof the processor and may transmit and receive data to and from theprocessor via various known means.

The detailed description of the preferred embodiments of the presentinvention is given to enable those skilled in the art to realize andimplement the present invention. While the present invention has beendescribed referring to the preferred embodiments of the presentinvention, those skilled in the art will appreciate that manymodifications and changes can be made to the present invention withoutdeparting from the spirit and essential characteristics of the presentinvention. For example, the structures of the above-describedembodiments of the present invention can be used in combination. Theabove embodiments are therefore to be construed in all aspects asillustrative and not restrictive. Therefore, the present inventionintends not to limit the embodiments disclosed herein but to give abroadest range matching the principles and new features disclosedherein.

Those skilled in the art will appreciate that the present invention maybe carried out in other specific ways than those set forth hereinwithout departing from the spirit and essential characteristics of thepresent invention. The above embodiments are therefore to be construedin all aspects as illustrative and not restrictive. The scope of theinvention should be determined by the appended claims and their legalequivalents, not by the above description, and all changes coming withinthe meaning and equivalency range of the appended claims are intended tobe embraced therein. Therefore, the present invention intends not tolimit the embodiments disclosed herein but to give a broadest rangematching the principles and new features disclosed herein. It is obviousto those skilled in the art that claims that are not explicitly cited ineach other in the appended claims may be presented in combination as anembodiment of the present invention or included as a new claim by asubsequent amendment after the application is filed.

INDUSTRIAL APPLICABILITY

The above-described embodiments of the present invention are applicableto various mobile communication systems.

1. A method for scheduling uplink multi-antenna transmission, the methodcomprising: generating Downlink Control Information (DCI) includingprecoding information indicating a transmission rank and a precodingmatrix for uplink transmission; transmitting the generated DCI forscheduling uplink transmission on a downlink control channel; andreceiving an uplink signal scheduled according to the DCI on an uplinkdata channel, wherein the size of the precoding information isdetermined according to the number of multiple antennas and the numberof precoding matrices available according to an uplink transmissionrank.
 2. The method according to claim 1, wherein if the number ofmultiple antennas is 2, the size of the precoding information is 3 bitsand if the number of multiple antennas is 4, the size of the precodinginformation is 6 bits.
 3. The method according to claim 1, wherein theprecoding information indicates a different transmission rank and adifferent precoding matrix according to the number of enabled codewords.4. The method according to claim 1, wherein for 2 multiple antennas, ifone codeword is enabled, the precoding information includes 6 statesindicating 6 precoding matrices for rank 1 and 2 reserved states, and iftwo codewords are enabled, the precoding information includes 1 stateindicating 1 precoding matrix for rank 2 and 7 reserved states.
 5. Themethod according to claim 1, wherein for 4 multiple antennas, if onecodeword is enabled, the precoding information includes 24 statesindicating 24 precoding matrices for rank 1, 16 states indicating 16precoding matrices for rank 2, and 24 reserved states, and if twocodewords are enabled, the precoding information includes 16 stateindicating 16 precoding matrix for rank 2, 12 states indicating 12precoding matrices for rank 3, 1 state indicating 1 precoding matrix forrank 4, and 35 reserved states.
 6. The method according to claim 1,wherein the downlink control channel is a Physical Downlink ControlChannel (PDCCH) and the uplink data channel is a Physical Uplink SharedChannel (PUSCH).
 7. A method for performing uplink multi-antennatransmission, the method comprising: receiving Downlink ControlInformation (DCI) including precoding information on a downlink controlchannel, the precoding information indicating a transmission rank and aprecoding matrix for uplink transmission; and transmitting an uplinksignal scheduled according to the DCI on an uplink data channel, whereinthe size of the precoding information is determined according to thenumber of multiple antennas and the number of precoding matricesavailable according to an uplink transmission rank.
 8. The methodaccording to claim 7, wherein if the number of multiple antennas is 2,the size of the precoding information is 3 bits and if the number ofmultiple antennas is 4, the size of the precoding information is 6 bits.9. The method according to claim 7, wherein the precoding informationindicates a different transmission rank and a different precoding matrixaccording to the number of enabled codewords.
 10. The method accordingto claim 7, wherein for 2 multiple antennas, if one codeword is enabled,the precoding information includes 6 states indicating 6 precodingmatrices for rank 1 and 2 reserved states, and if two codewords areenabled, the precoding information includes 1 state indicating 1precoding matrix for rank 2 and 7 reserved states.
 11. The methodaccording to claim 7, wherein for 4 multiple antennas, if one codewordis enabled, the precoding information includes 24 states indicating 24precoding matrices for rank 1, 16 states indicating 16 precodingmatrices for rank 2, and 24 reserved states, and if two codewords areenabled, the precoding information includes 16 state indicating 16precoding matrix for rank 2, 12 states indicating 12 precoding matricesfor rank 3, 1 state indicating 1 precoding matrix for rank 4, and 35reserved states.
 12. The method according to claim 7, wherein thedownlink control channel is a Physical Downlink Control Channel (PDCCH)and the uplink data channel is a Physical Uplink Shared Channel (PUSCH).13. A base station for scheduling uplink multi-antenna transmission, thebase station comprising: a transmission module for transmitting adownlink signal to a user equipment; a reception module for receiving anuplink signal from the user equipment; and a processor for controllingthe base station including the reception module and the transmissionmodule, wherein the processor is configured to generate Downlink ControlInformation (DCI) including precoding information indicating atransmission rank and a precoding matrix for uplink transmission,transmit the generated DCI for scheduling uplink transmission on adownlink control channel through the transmission module, and receive anuplink signal scheduled according to the DCI on an uplink data channelthrough the reception module, wherein the size of the precodinginformation is determined according to the number of multiple antennasand the number of precoding matrices available according to an uplinktransmission rank.
 14. A user equipment for performing uplinkmulti-antenna transmission, the user equipment comprising: atransmission module for transmitting an uplink signal to a base station;a reception module for receiving a downlink signal from the basestation; and a processor for controlling the user equipment includingthe transmission module and the reception module, wherein the processoris configured to receive Downlink Control Information (DCI) includingprecoding information on a downlink control channel through thereception module, the precoding information indicating a transmissionrank and a precoding matrix for uplink transmission and transmit anuplink signal scheduled according to the DCI on an uplink data channelthrough the transmission module, wherein the size of the precodinginformation is determined according to the number of multiple antennasand the number of precoding matrices available according to an uplinktransmission rank.